Reporting new USB storage devices on Linux and macOS with Python












6












$begingroup$


Synopsis:



I wanted something for macOS (and Linux; maybe eventually Windows) that would simply wait for the user to connect a storage device and automatically select, or otherwise output the information to be used, read, manipulated, etc.



In its current form, it just prints to the shell, but you could assign the output to a list or variable for read/write operations and so on. It will respond to any new entries in the /dev system directory, including most USB devices, SD Cards, Webcams, and so on. You can test it by running the script in one window, and running something like sudo touch /dev/{x,y,z} in another.



I plan to use it to help people (those of us who are less technically inclined) migrate to Linux by automating the creation of bootable flash drives, but you can do what you like with it.



Open-ended feedback and suggestions are welcome. Please try to post example code pertaining to your suggestions, and don't be afraid to say something positive.



Usage:



user@macOS:~$ ./devlisten.py
/dev/disk2
/dev/rdisk2
/dev/disk2s1
/dev/rdisk2s1


Code:



#!/usr/bin/env python3

import os
import re
import time
import difflib

try:
os.mkdir('/tmp/dev')
except FileExistsError:
pass
except FileNotFoundError:
print('No /tmp directory found.')
exit()
except OSError:
print('Read-only file system.')
exit()

file1 = open('/tmp/dev/1', 'w')
for x in os.listdir('/dev'):
file1.write(x + 'n')
file1.close()

try:

diff = False
while diff == False:
time.sleep(0.25)

file2 = open('/tmp/dev/2', 'w')
for x in os.listdir('/dev'):
file2.write(x + 'n')
file2.close()

text1 = open('/tmp/dev/1').readlines()
text2 = open('/tmp/dev/2').readlines()

for line in difflib.unified_diff(text1, text2):
for line in re.finditer(r'(?<=^+)w.*$', line, re.MULTILINE):
print('/dev/' + line.group(0))
diff = True

except KeyboardInterrupt:

print()
exit()









share|improve this question











$endgroup$

















    6












    $begingroup$


    Synopsis:



    I wanted something for macOS (and Linux; maybe eventually Windows) that would simply wait for the user to connect a storage device and automatically select, or otherwise output the information to be used, read, manipulated, etc.



    In its current form, it just prints to the shell, but you could assign the output to a list or variable for read/write operations and so on. It will respond to any new entries in the /dev system directory, including most USB devices, SD Cards, Webcams, and so on. You can test it by running the script in one window, and running something like sudo touch /dev/{x,y,z} in another.



    I plan to use it to help people (those of us who are less technically inclined) migrate to Linux by automating the creation of bootable flash drives, but you can do what you like with it.



    Open-ended feedback and suggestions are welcome. Please try to post example code pertaining to your suggestions, and don't be afraid to say something positive.



    Usage:



    user@macOS:~$ ./devlisten.py
    /dev/disk2
    /dev/rdisk2
    /dev/disk2s1
    /dev/rdisk2s1


    Code:



    #!/usr/bin/env python3

    import os
    import re
    import time
    import difflib

    try:
    os.mkdir('/tmp/dev')
    except FileExistsError:
    pass
    except FileNotFoundError:
    print('No /tmp directory found.')
    exit()
    except OSError:
    print('Read-only file system.')
    exit()

    file1 = open('/tmp/dev/1', 'w')
    for x in os.listdir('/dev'):
    file1.write(x + 'n')
    file1.close()

    try:

    diff = False
    while diff == False:
    time.sleep(0.25)

    file2 = open('/tmp/dev/2', 'w')
    for x in os.listdir('/dev'):
    file2.write(x + 'n')
    file2.close()

    text1 = open('/tmp/dev/1').readlines()
    text2 = open('/tmp/dev/2').readlines()

    for line in difflib.unified_diff(text1, text2):
    for line in re.finditer(r'(?<=^+)w.*$', line, re.MULTILINE):
    print('/dev/' + line.group(0))
    diff = True

    except KeyboardInterrupt:

    print()
    exit()









    share|improve this question











    $endgroup$















      6












      6








      6


      2



      $begingroup$


      Synopsis:



      I wanted something for macOS (and Linux; maybe eventually Windows) that would simply wait for the user to connect a storage device and automatically select, or otherwise output the information to be used, read, manipulated, etc.



      In its current form, it just prints to the shell, but you could assign the output to a list or variable for read/write operations and so on. It will respond to any new entries in the /dev system directory, including most USB devices, SD Cards, Webcams, and so on. You can test it by running the script in one window, and running something like sudo touch /dev/{x,y,z} in another.



      I plan to use it to help people (those of us who are less technically inclined) migrate to Linux by automating the creation of bootable flash drives, but you can do what you like with it.



      Open-ended feedback and suggestions are welcome. Please try to post example code pertaining to your suggestions, and don't be afraid to say something positive.



      Usage:



      user@macOS:~$ ./devlisten.py
      /dev/disk2
      /dev/rdisk2
      /dev/disk2s1
      /dev/rdisk2s1


      Code:



      #!/usr/bin/env python3

      import os
      import re
      import time
      import difflib

      try:
      os.mkdir('/tmp/dev')
      except FileExistsError:
      pass
      except FileNotFoundError:
      print('No /tmp directory found.')
      exit()
      except OSError:
      print('Read-only file system.')
      exit()

      file1 = open('/tmp/dev/1', 'w')
      for x in os.listdir('/dev'):
      file1.write(x + 'n')
      file1.close()

      try:

      diff = False
      while diff == False:
      time.sleep(0.25)

      file2 = open('/tmp/dev/2', 'w')
      for x in os.listdir('/dev'):
      file2.write(x + 'n')
      file2.close()

      text1 = open('/tmp/dev/1').readlines()
      text2 = open('/tmp/dev/2').readlines()

      for line in difflib.unified_diff(text1, text2):
      for line in re.finditer(r'(?<=^+)w.*$', line, re.MULTILINE):
      print('/dev/' + line.group(0))
      diff = True

      except KeyboardInterrupt:

      print()
      exit()









      share|improve this question











      $endgroup$




      Synopsis:



      I wanted something for macOS (and Linux; maybe eventually Windows) that would simply wait for the user to connect a storage device and automatically select, or otherwise output the information to be used, read, manipulated, etc.



      In its current form, it just prints to the shell, but you could assign the output to a list or variable for read/write operations and so on. It will respond to any new entries in the /dev system directory, including most USB devices, SD Cards, Webcams, and so on. You can test it by running the script in one window, and running something like sudo touch /dev/{x,y,z} in another.



      I plan to use it to help people (those of us who are less technically inclined) migrate to Linux by automating the creation of bootable flash drives, but you can do what you like with it.



      Open-ended feedback and suggestions are welcome. Please try to post example code pertaining to your suggestions, and don't be afraid to say something positive.



      Usage:



      user@macOS:~$ ./devlisten.py
      /dev/disk2
      /dev/rdisk2
      /dev/disk2s1
      /dev/rdisk2s1


      Code:



      #!/usr/bin/env python3

      import os
      import re
      import time
      import difflib

      try:
      os.mkdir('/tmp/dev')
      except FileExistsError:
      pass
      except FileNotFoundError:
      print('No /tmp directory found.')
      exit()
      except OSError:
      print('Read-only file system.')
      exit()

      file1 = open('/tmp/dev/1', 'w')
      for x in os.listdir('/dev'):
      file1.write(x + 'n')
      file1.close()

      try:

      diff = False
      while diff == False:
      time.sleep(0.25)

      file2 = open('/tmp/dev/2', 'w')
      for x in os.listdir('/dev'):
      file2.write(x + 'n')
      file2.close()

      text1 = open('/tmp/dev/1').readlines()
      text2 = open('/tmp/dev/2').readlines()

      for line in difflib.unified_diff(text1, text2):
      for line in re.finditer(r'(?<=^+)w.*$', line, re.MULTILINE):
      print('/dev/' + line.group(0))
      diff = True

      except KeyboardInterrupt:

      print()
      exit()






      python beginner python-3.x linux macos






      share|improve this question















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      share|improve this question




      share|improve this question








      edited 11 hours ago









      200_success

      129k15152414




      129k15152414










      asked 15 hours ago









      tjt263tjt263

      32437




      32437






















          4 Answers
          4






          active

          oldest

          votes


















          8












          $begingroup$

          This script might get the job done, but it is a rather crude and inefficient hack. Ideally, you should avoid polling every quarter second (or polling at all). Also, I see no reason to write any files to /tmp.





          The ideal way to do it in Linux is to use udev. If you don't want to write a persistent udev rule, or you don't have root access, you can run /sbin/udevadm monitor --udev --property as a child process, and trigger your test whenever udevadm offers output. For a smarter script, you can can look for the ACTION=add line and take advantage of the information in the SUBSYSTEM=… and DEVPATH=… lines. DEVPATH tells you path to the device within /sys. But, even if you simply trigger your script only when any output appears, that would be a huge improvement over polling four times a second.



          import itertools
          from subprocess import Popen, PIPE
          import re
          import sys

          KEYVALUE_RE = re.compile(r'([^=]+)=(.*)')

          def events(stream):
          """
          Read udev events from the stream, yielding them as dictionaries.
          """
          while True:
          event = dict(
          KEYVALUE_RE.match(line).groups()
          for line in itertools.takewhile(KEYVALUE_RE.match, stream)
          )
          if event:
          yield event

          try:
          UDEVADM = ['/sbin/udevadm', 'monitor', '--udev', '--property']
          with Popen(UDEVADM, stdout=PIPE, encoding='UTF-8') as udevadm:
          for event in events(udevadm.stdout):
          if event['ACTION'] == 'add' and event.get('DRIVER') == 'usb-storage':
          print(event)
          break
          except KeyboardInterrupt:
          sys.exit(1)




          On macOS, you can get similar information by running and monitoring the output of /usr/sbin/diskutil activity, if you are interested in storage devices. Look for lines starting with ***DiskAppeared.



          from subprocess import Popen, PIPE
          import sys

          try:
          DISKUTIL = ['/usr/sbin/diskutil', 'activity']
          with Popen(DISKUTIL, stdout=PIPE, encoding='UTF-8') as diskutil:
          # Ignore events that describe the present state
          for line in diskutil.stdout:
          if line.startswith('***DAIdle'):
          break
          # Detect the first subsequent "Disk Appeared" event
          for line in diskutil.stdout:
          if line.startswith('***DiskAppeared'):
          print(line)
          break
          except KeyboardInterrupt:
          sys.exit(1)


          If you are interested in non-storage devices as well, then you could take advantage of the File System Events API, possibly through the MacFSEvents Python package or the cross-platform fswatch program.






          share|improve this answer











          $endgroup$













          • $begingroup$
            Thanks for the feedback. It doesn't have to be poll @ 4Hz, but it's only intended to be run for seconds at a time. If you could show some python code pertaining to your suggestions, that would be super helpful. You seem to know what you're talking about, but it's all very unfamiliar to me.
            $endgroup$
            – tjt263
            9 hours ago



















          5












          $begingroup$

          Prefer to use $TMPDIR if set, and /tmp only as a fallback. That's the standard practice that allows users to have separate, private temporary directories, for example, so don't subvert it! You probably ought to consider tempfile.​TemporaryDirectory() as an alternative.



          Error messages should go to standard error channel, not standard output.



          I don't know Mac OS, but on Linux I'd expect you to wait on inotify, rather than polling the dev directory. There's a choice of Python interface to inotify, but I'm not in a position to recommend any in particular.






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            macOS has FSEvents (en.wikipedia.org/wiki/FSEvents). I don't know much about it.
            $endgroup$
            – tjt263
            10 hours ago



















          5












          $begingroup$



          • context managers



            You should really open and close files with the with statement see PEP343




          • if __name__ == '__main__': guard



            Python idiom is to use a guard to ensure main is not run when being imported by another script




          • tempfile



            As mentioned by @Toby already, there is module for creating Temporary files/directories




          • Why does it need to be in a file though?



            You could create a list of filenames and poll for changes



            And compare the lists instead of the files








          share|improve this answer









          $endgroup$













          • $begingroup$
            It doesn't have to be stored in a file. I just thought it would be better than storing it in RAM the whole time.
            $endgroup$
            – tjt263
            10 hours ago






          • 1




            $begingroup$
            @tjt263 Why would it?
            $endgroup$
            – Konrad Rudolph
            4 hours ago



















          3












          $begingroup$

          Another point I didn't see mentioned:



          try:
          os.mkdir('/tmp/dev')
          except FileExistsError:
          pass


          except blocks with pass are usually a sign that there is probably a better way. In this case, assuming you are using Python 3.2 or later, is to use os.makedirs with the exist_ok argument set to True:



          os.makedirs('/tmp/dev', exist_ok=True)





          share|improve this answer









          $endgroup$













          • $begingroup$
            Why's that better? What's the difference?
            $endgroup$
            – tjt263
            6 hours ago











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          4 Answers
          4






          active

          oldest

          votes








          4 Answers
          4






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          8












          $begingroup$

          This script might get the job done, but it is a rather crude and inefficient hack. Ideally, you should avoid polling every quarter second (or polling at all). Also, I see no reason to write any files to /tmp.





          The ideal way to do it in Linux is to use udev. If you don't want to write a persistent udev rule, or you don't have root access, you can run /sbin/udevadm monitor --udev --property as a child process, and trigger your test whenever udevadm offers output. For a smarter script, you can can look for the ACTION=add line and take advantage of the information in the SUBSYSTEM=… and DEVPATH=… lines. DEVPATH tells you path to the device within /sys. But, even if you simply trigger your script only when any output appears, that would be a huge improvement over polling four times a second.



          import itertools
          from subprocess import Popen, PIPE
          import re
          import sys

          KEYVALUE_RE = re.compile(r'([^=]+)=(.*)')

          def events(stream):
          """
          Read udev events from the stream, yielding them as dictionaries.
          """
          while True:
          event = dict(
          KEYVALUE_RE.match(line).groups()
          for line in itertools.takewhile(KEYVALUE_RE.match, stream)
          )
          if event:
          yield event

          try:
          UDEVADM = ['/sbin/udevadm', 'monitor', '--udev', '--property']
          with Popen(UDEVADM, stdout=PIPE, encoding='UTF-8') as udevadm:
          for event in events(udevadm.stdout):
          if event['ACTION'] == 'add' and event.get('DRIVER') == 'usb-storage':
          print(event)
          break
          except KeyboardInterrupt:
          sys.exit(1)




          On macOS, you can get similar information by running and monitoring the output of /usr/sbin/diskutil activity, if you are interested in storage devices. Look for lines starting with ***DiskAppeared.



          from subprocess import Popen, PIPE
          import sys

          try:
          DISKUTIL = ['/usr/sbin/diskutil', 'activity']
          with Popen(DISKUTIL, stdout=PIPE, encoding='UTF-8') as diskutil:
          # Ignore events that describe the present state
          for line in diskutil.stdout:
          if line.startswith('***DAIdle'):
          break
          # Detect the first subsequent "Disk Appeared" event
          for line in diskutil.stdout:
          if line.startswith('***DiskAppeared'):
          print(line)
          break
          except KeyboardInterrupt:
          sys.exit(1)


          If you are interested in non-storage devices as well, then you could take advantage of the File System Events API, possibly through the MacFSEvents Python package or the cross-platform fswatch program.






          share|improve this answer











          $endgroup$













          • $begingroup$
            Thanks for the feedback. It doesn't have to be poll @ 4Hz, but it's only intended to be run for seconds at a time. If you could show some python code pertaining to your suggestions, that would be super helpful. You seem to know what you're talking about, but it's all very unfamiliar to me.
            $endgroup$
            – tjt263
            9 hours ago
















          8












          $begingroup$

          This script might get the job done, but it is a rather crude and inefficient hack. Ideally, you should avoid polling every quarter second (or polling at all). Also, I see no reason to write any files to /tmp.





          The ideal way to do it in Linux is to use udev. If you don't want to write a persistent udev rule, or you don't have root access, you can run /sbin/udevadm monitor --udev --property as a child process, and trigger your test whenever udevadm offers output. For a smarter script, you can can look for the ACTION=add line and take advantage of the information in the SUBSYSTEM=… and DEVPATH=… lines. DEVPATH tells you path to the device within /sys. But, even if you simply trigger your script only when any output appears, that would be a huge improvement over polling four times a second.



          import itertools
          from subprocess import Popen, PIPE
          import re
          import sys

          KEYVALUE_RE = re.compile(r'([^=]+)=(.*)')

          def events(stream):
          """
          Read udev events from the stream, yielding them as dictionaries.
          """
          while True:
          event = dict(
          KEYVALUE_RE.match(line).groups()
          for line in itertools.takewhile(KEYVALUE_RE.match, stream)
          )
          if event:
          yield event

          try:
          UDEVADM = ['/sbin/udevadm', 'monitor', '--udev', '--property']
          with Popen(UDEVADM, stdout=PIPE, encoding='UTF-8') as udevadm:
          for event in events(udevadm.stdout):
          if event['ACTION'] == 'add' and event.get('DRIVER') == 'usb-storage':
          print(event)
          break
          except KeyboardInterrupt:
          sys.exit(1)




          On macOS, you can get similar information by running and monitoring the output of /usr/sbin/diskutil activity, if you are interested in storage devices. Look for lines starting with ***DiskAppeared.



          from subprocess import Popen, PIPE
          import sys

          try:
          DISKUTIL = ['/usr/sbin/diskutil', 'activity']
          with Popen(DISKUTIL, stdout=PIPE, encoding='UTF-8') as diskutil:
          # Ignore events that describe the present state
          for line in diskutil.stdout:
          if line.startswith('***DAIdle'):
          break
          # Detect the first subsequent "Disk Appeared" event
          for line in diskutil.stdout:
          if line.startswith('***DiskAppeared'):
          print(line)
          break
          except KeyboardInterrupt:
          sys.exit(1)


          If you are interested in non-storage devices as well, then you could take advantage of the File System Events API, possibly through the MacFSEvents Python package or the cross-platform fswatch program.






          share|improve this answer











          $endgroup$













          • $begingroup$
            Thanks for the feedback. It doesn't have to be poll @ 4Hz, but it's only intended to be run for seconds at a time. If you could show some python code pertaining to your suggestions, that would be super helpful. You seem to know what you're talking about, but it's all very unfamiliar to me.
            $endgroup$
            – tjt263
            9 hours ago














          8












          8








          8





          $begingroup$

          This script might get the job done, but it is a rather crude and inefficient hack. Ideally, you should avoid polling every quarter second (or polling at all). Also, I see no reason to write any files to /tmp.





          The ideal way to do it in Linux is to use udev. If you don't want to write a persistent udev rule, or you don't have root access, you can run /sbin/udevadm monitor --udev --property as a child process, and trigger your test whenever udevadm offers output. For a smarter script, you can can look for the ACTION=add line and take advantage of the information in the SUBSYSTEM=… and DEVPATH=… lines. DEVPATH tells you path to the device within /sys. But, even if you simply trigger your script only when any output appears, that would be a huge improvement over polling four times a second.



          import itertools
          from subprocess import Popen, PIPE
          import re
          import sys

          KEYVALUE_RE = re.compile(r'([^=]+)=(.*)')

          def events(stream):
          """
          Read udev events from the stream, yielding them as dictionaries.
          """
          while True:
          event = dict(
          KEYVALUE_RE.match(line).groups()
          for line in itertools.takewhile(KEYVALUE_RE.match, stream)
          )
          if event:
          yield event

          try:
          UDEVADM = ['/sbin/udevadm', 'monitor', '--udev', '--property']
          with Popen(UDEVADM, stdout=PIPE, encoding='UTF-8') as udevadm:
          for event in events(udevadm.stdout):
          if event['ACTION'] == 'add' and event.get('DRIVER') == 'usb-storage':
          print(event)
          break
          except KeyboardInterrupt:
          sys.exit(1)




          On macOS, you can get similar information by running and monitoring the output of /usr/sbin/diskutil activity, if you are interested in storage devices. Look for lines starting with ***DiskAppeared.



          from subprocess import Popen, PIPE
          import sys

          try:
          DISKUTIL = ['/usr/sbin/diskutil', 'activity']
          with Popen(DISKUTIL, stdout=PIPE, encoding='UTF-8') as diskutil:
          # Ignore events that describe the present state
          for line in diskutil.stdout:
          if line.startswith('***DAIdle'):
          break
          # Detect the first subsequent "Disk Appeared" event
          for line in diskutil.stdout:
          if line.startswith('***DiskAppeared'):
          print(line)
          break
          except KeyboardInterrupt:
          sys.exit(1)


          If you are interested in non-storage devices as well, then you could take advantage of the File System Events API, possibly through the MacFSEvents Python package or the cross-platform fswatch program.






          share|improve this answer











          $endgroup$



          This script might get the job done, but it is a rather crude and inefficient hack. Ideally, you should avoid polling every quarter second (or polling at all). Also, I see no reason to write any files to /tmp.





          The ideal way to do it in Linux is to use udev. If you don't want to write a persistent udev rule, or you don't have root access, you can run /sbin/udevadm monitor --udev --property as a child process, and trigger your test whenever udevadm offers output. For a smarter script, you can can look for the ACTION=add line and take advantage of the information in the SUBSYSTEM=… and DEVPATH=… lines. DEVPATH tells you path to the device within /sys. But, even if you simply trigger your script only when any output appears, that would be a huge improvement over polling four times a second.



          import itertools
          from subprocess import Popen, PIPE
          import re
          import sys

          KEYVALUE_RE = re.compile(r'([^=]+)=(.*)')

          def events(stream):
          """
          Read udev events from the stream, yielding them as dictionaries.
          """
          while True:
          event = dict(
          KEYVALUE_RE.match(line).groups()
          for line in itertools.takewhile(KEYVALUE_RE.match, stream)
          )
          if event:
          yield event

          try:
          UDEVADM = ['/sbin/udevadm', 'monitor', '--udev', '--property']
          with Popen(UDEVADM, stdout=PIPE, encoding='UTF-8') as udevadm:
          for event in events(udevadm.stdout):
          if event['ACTION'] == 'add' and event.get('DRIVER') == 'usb-storage':
          print(event)
          break
          except KeyboardInterrupt:
          sys.exit(1)




          On macOS, you can get similar information by running and monitoring the output of /usr/sbin/diskutil activity, if you are interested in storage devices. Look for lines starting with ***DiskAppeared.



          from subprocess import Popen, PIPE
          import sys

          try:
          DISKUTIL = ['/usr/sbin/diskutil', 'activity']
          with Popen(DISKUTIL, stdout=PIPE, encoding='UTF-8') as diskutil:
          # Ignore events that describe the present state
          for line in diskutil.stdout:
          if line.startswith('***DAIdle'):
          break
          # Detect the first subsequent "Disk Appeared" event
          for line in diskutil.stdout:
          if line.startswith('***DiskAppeared'):
          print(line)
          break
          except KeyboardInterrupt:
          sys.exit(1)


          If you are interested in non-storage devices as well, then you could take advantage of the File System Events API, possibly through the MacFSEvents Python package or the cross-platform fswatch program.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 8 hours ago

























          answered 10 hours ago









          200_success200_success

          129k15152414




          129k15152414












          • $begingroup$
            Thanks for the feedback. It doesn't have to be poll @ 4Hz, but it's only intended to be run for seconds at a time. If you could show some python code pertaining to your suggestions, that would be super helpful. You seem to know what you're talking about, but it's all very unfamiliar to me.
            $endgroup$
            – tjt263
            9 hours ago


















          • $begingroup$
            Thanks for the feedback. It doesn't have to be poll @ 4Hz, but it's only intended to be run for seconds at a time. If you could show some python code pertaining to your suggestions, that would be super helpful. You seem to know what you're talking about, but it's all very unfamiliar to me.
            $endgroup$
            – tjt263
            9 hours ago
















          $begingroup$
          Thanks for the feedback. It doesn't have to be poll @ 4Hz, but it's only intended to be run for seconds at a time. If you could show some python code pertaining to your suggestions, that would be super helpful. You seem to know what you're talking about, but it's all very unfamiliar to me.
          $endgroup$
          – tjt263
          9 hours ago




          $begingroup$
          Thanks for the feedback. It doesn't have to be poll @ 4Hz, but it's only intended to be run for seconds at a time. If you could show some python code pertaining to your suggestions, that would be super helpful. You seem to know what you're talking about, but it's all very unfamiliar to me.
          $endgroup$
          – tjt263
          9 hours ago













          5












          $begingroup$

          Prefer to use $TMPDIR if set, and /tmp only as a fallback. That's the standard practice that allows users to have separate, private temporary directories, for example, so don't subvert it! You probably ought to consider tempfile.​TemporaryDirectory() as an alternative.



          Error messages should go to standard error channel, not standard output.



          I don't know Mac OS, but on Linux I'd expect you to wait on inotify, rather than polling the dev directory. There's a choice of Python interface to inotify, but I'm not in a position to recommend any in particular.






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            macOS has FSEvents (en.wikipedia.org/wiki/FSEvents). I don't know much about it.
            $endgroup$
            – tjt263
            10 hours ago
















          5












          $begingroup$

          Prefer to use $TMPDIR if set, and /tmp only as a fallback. That's the standard practice that allows users to have separate, private temporary directories, for example, so don't subvert it! You probably ought to consider tempfile.​TemporaryDirectory() as an alternative.



          Error messages should go to standard error channel, not standard output.



          I don't know Mac OS, but on Linux I'd expect you to wait on inotify, rather than polling the dev directory. There's a choice of Python interface to inotify, but I'm not in a position to recommend any in particular.






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            macOS has FSEvents (en.wikipedia.org/wiki/FSEvents). I don't know much about it.
            $endgroup$
            – tjt263
            10 hours ago














          5












          5








          5





          $begingroup$

          Prefer to use $TMPDIR if set, and /tmp only as a fallback. That's the standard practice that allows users to have separate, private temporary directories, for example, so don't subvert it! You probably ought to consider tempfile.​TemporaryDirectory() as an alternative.



          Error messages should go to standard error channel, not standard output.



          I don't know Mac OS, but on Linux I'd expect you to wait on inotify, rather than polling the dev directory. There's a choice of Python interface to inotify, but I'm not in a position to recommend any in particular.






          share|improve this answer









          $endgroup$



          Prefer to use $TMPDIR if set, and /tmp only as a fallback. That's the standard practice that allows users to have separate, private temporary directories, for example, so don't subvert it! You probably ought to consider tempfile.​TemporaryDirectory() as an alternative.



          Error messages should go to standard error channel, not standard output.



          I don't know Mac OS, but on Linux I'd expect you to wait on inotify, rather than polling the dev directory. There's a choice of Python interface to inotify, but I'm not in a position to recommend any in particular.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 14 hours ago









          Toby SpeightToby Speight

          23.8k639113




          23.8k639113








          • 1




            $begingroup$
            macOS has FSEvents (en.wikipedia.org/wiki/FSEvents). I don't know much about it.
            $endgroup$
            – tjt263
            10 hours ago














          • 1




            $begingroup$
            macOS has FSEvents (en.wikipedia.org/wiki/FSEvents). I don't know much about it.
            $endgroup$
            – tjt263
            10 hours ago








          1




          1




          $begingroup$
          macOS has FSEvents (en.wikipedia.org/wiki/FSEvents). I don't know much about it.
          $endgroup$
          – tjt263
          10 hours ago




          $begingroup$
          macOS has FSEvents (en.wikipedia.org/wiki/FSEvents). I don't know much about it.
          $endgroup$
          – tjt263
          10 hours ago











          5












          $begingroup$



          • context managers



            You should really open and close files with the with statement see PEP343




          • if __name__ == '__main__': guard



            Python idiom is to use a guard to ensure main is not run when being imported by another script




          • tempfile



            As mentioned by @Toby already, there is module for creating Temporary files/directories




          • Why does it need to be in a file though?



            You could create a list of filenames and poll for changes



            And compare the lists instead of the files








          share|improve this answer









          $endgroup$













          • $begingroup$
            It doesn't have to be stored in a file. I just thought it would be better than storing it in RAM the whole time.
            $endgroup$
            – tjt263
            10 hours ago






          • 1




            $begingroup$
            @tjt263 Why would it?
            $endgroup$
            – Konrad Rudolph
            4 hours ago
















          5












          $begingroup$



          • context managers



            You should really open and close files with the with statement see PEP343




          • if __name__ == '__main__': guard



            Python idiom is to use a guard to ensure main is not run when being imported by another script




          • tempfile



            As mentioned by @Toby already, there is module for creating Temporary files/directories




          • Why does it need to be in a file though?



            You could create a list of filenames and poll for changes



            And compare the lists instead of the files








          share|improve this answer









          $endgroup$













          • $begingroup$
            It doesn't have to be stored in a file. I just thought it would be better than storing it in RAM the whole time.
            $endgroup$
            – tjt263
            10 hours ago






          • 1




            $begingroup$
            @tjt263 Why would it?
            $endgroup$
            – Konrad Rudolph
            4 hours ago














          5












          5








          5





          $begingroup$



          • context managers



            You should really open and close files with the with statement see PEP343




          • if __name__ == '__main__': guard



            Python idiom is to use a guard to ensure main is not run when being imported by another script




          • tempfile



            As mentioned by @Toby already, there is module for creating Temporary files/directories




          • Why does it need to be in a file though?



            You could create a list of filenames and poll for changes



            And compare the lists instead of the files








          share|improve this answer









          $endgroup$





          • context managers



            You should really open and close files with the with statement see PEP343




          • if __name__ == '__main__': guard



            Python idiom is to use a guard to ensure main is not run when being imported by another script




          • tempfile



            As mentioned by @Toby already, there is module for creating Temporary files/directories




          • Why does it need to be in a file though?



            You could create a list of filenames and poll for changes



            And compare the lists instead of the files









          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 14 hours ago









          LudisposedLudisposed

          7,27421959




          7,27421959












          • $begingroup$
            It doesn't have to be stored in a file. I just thought it would be better than storing it in RAM the whole time.
            $endgroup$
            – tjt263
            10 hours ago






          • 1




            $begingroup$
            @tjt263 Why would it?
            $endgroup$
            – Konrad Rudolph
            4 hours ago


















          • $begingroup$
            It doesn't have to be stored in a file. I just thought it would be better than storing it in RAM the whole time.
            $endgroup$
            – tjt263
            10 hours ago






          • 1




            $begingroup$
            @tjt263 Why would it?
            $endgroup$
            – Konrad Rudolph
            4 hours ago
















          $begingroup$
          It doesn't have to be stored in a file. I just thought it would be better than storing it in RAM the whole time.
          $endgroup$
          – tjt263
          10 hours ago




          $begingroup$
          It doesn't have to be stored in a file. I just thought it would be better than storing it in RAM the whole time.
          $endgroup$
          – tjt263
          10 hours ago




          1




          1




          $begingroup$
          @tjt263 Why would it?
          $endgroup$
          – Konrad Rudolph
          4 hours ago




          $begingroup$
          @tjt263 Why would it?
          $endgroup$
          – Konrad Rudolph
          4 hours ago











          3












          $begingroup$

          Another point I didn't see mentioned:



          try:
          os.mkdir('/tmp/dev')
          except FileExistsError:
          pass


          except blocks with pass are usually a sign that there is probably a better way. In this case, assuming you are using Python 3.2 or later, is to use os.makedirs with the exist_ok argument set to True:



          os.makedirs('/tmp/dev', exist_ok=True)





          share|improve this answer









          $endgroup$













          • $begingroup$
            Why's that better? What's the difference?
            $endgroup$
            – tjt263
            6 hours ago
















          3












          $begingroup$

          Another point I didn't see mentioned:



          try:
          os.mkdir('/tmp/dev')
          except FileExistsError:
          pass


          except blocks with pass are usually a sign that there is probably a better way. In this case, assuming you are using Python 3.2 or later, is to use os.makedirs with the exist_ok argument set to True:



          os.makedirs('/tmp/dev', exist_ok=True)





          share|improve this answer









          $endgroup$













          • $begingroup$
            Why's that better? What's the difference?
            $endgroup$
            – tjt263
            6 hours ago














          3












          3








          3





          $begingroup$

          Another point I didn't see mentioned:



          try:
          os.mkdir('/tmp/dev')
          except FileExistsError:
          pass


          except blocks with pass are usually a sign that there is probably a better way. In this case, assuming you are using Python 3.2 or later, is to use os.makedirs with the exist_ok argument set to True:



          os.makedirs('/tmp/dev', exist_ok=True)





          share|improve this answer









          $endgroup$



          Another point I didn't see mentioned:



          try:
          os.mkdir('/tmp/dev')
          except FileExistsError:
          pass


          except blocks with pass are usually a sign that there is probably a better way. In this case, assuming you are using Python 3.2 or later, is to use os.makedirs with the exist_ok argument set to True:



          os.makedirs('/tmp/dev', exist_ok=True)






          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 9 hours ago









          DeepSpaceDeepSpace

          28519




          28519












          • $begingroup$
            Why's that better? What's the difference?
            $endgroup$
            – tjt263
            6 hours ago


















          • $begingroup$
            Why's that better? What's the difference?
            $endgroup$
            – tjt263
            6 hours ago
















          $begingroup$
          Why's that better? What's the difference?
          $endgroup$
          – tjt263
          6 hours ago




          $begingroup$
          Why's that better? What's the difference?
          $endgroup$
          – tjt263
          6 hours ago


















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