How to implement common bash idioms in Python

Question

I currently do my textfile manipulation through a bunch of badly remembered AWK  sed  Bash and a tiny bit of Perl   I ve seen mentioned a few places that python is good for this kind of thing  How can I use Python to replace shell scripting  AWK  sed and friends

User · Answer

I suggest the awesome online book Dive Into Python   It s how I learned the language originally   Beyond teaching you the basic structure of the language  and a whole lot of useful data structures  it has a good chapter on file handling and subsequent chapters on regular expressions and more

User · Answer

I just discovered how to combine the best parts of bash and ipython  Up to now this seems more comfortable to me than using subprocess and so on  You can easily copy big parts of existing bash scripts and e g  add error handling in the python way    And here is my result      usr bin env ipython3        How to have the most comfort scripting experience of your life                                                                                      by using ipython for scripting combined with subcommands from bash      1  echo     usr bin env ipython3   gt  scriptname ipy      creates new ipy-file     2  chmod  x scriptname ipy                              make in executable     3  starting with line 2  write normal python or do some of      the   magic of ipython  so that you can use unix commands      within python and even assign their output to a variable via      var    cmd1   cmd2   cmd3                            enjoy        4  run via   scriptname ipy - if it fails with recognizing   and        but parses raw python fine  please check again for the  ipy suffix    ugly example  please go and find more in the wild files    ls       grep  y  for file in files     echo  file   grep  p    sorry for this nonsense example      See IPython docs on system shell commands and using it as a system shell

User · Answer

If you want to use Python as a shell  why not have a look at IPython   It is also good to learn interactively the language  If you do a lot of text manipulation  and if you use Vim as a text editor  you can also directly write plugins for Vim in python  just type   help python  in Vim and follow the instructions or have a look at this presentation  It is so easy and powerfull to write functions that you will use directly in your editor

User · Answer

If your textfile manipulation usually is one-time  possibly done on the shell-prompt  you will not get anything better from python   On the other hand  if you usually have to do the same  or similar  task over and over  and you have to write your scripts for doing that  then python is great - and you can easily create your own libraries  you can do that with shell scripts too  but it s more cumbersome    A very simple example to get a feeling   import popen2 stdout text  stdin text popen2 popen2  your-shell-command-here   for line in stdout text    if line startswith           pass   else     jobID int line split      0  split   1  lstrip   lt    rstrip   gt           do something with jobID   Check also sys and getopt module  they are the first you will need

User · Answer

In the beginning there was sh  sed  and awk  and find  and grep  and      It was good  But awk can be an odd little beast and hard to remember if you don t use it often  Then the great camel created Perl  Perl was a system administrator s dream  It was like shell scripting on steroids  Text processing  including regular expressions were just part of the language  Then it got ugly     People tried to make big applications with Perl  Now  don t get me wrong  Perl can be an application  but it can  can   look like a mess if you re not really careful  Then there is all this flat data business  It s enough to drive a programmer nuts   Enter Python  Ruby  et al  These are really very good general purpose languages  They support text processing  and do it well  though perhaps not as tightly entwined in the basic core of the language   But they also scale up very well  and still have nice looking code at the end of the day  They also have developed pretty hefty communities with plenty of libraries for most anything   Now  much of the negativeness towards Perl is a matter of opinion  and certainly some people can write very clean Perl  but with this many people complaining about it being too easy to create obfuscated code  you know some grain of truth is there  The question really becomes then  are you ever going to use this language for more than simple bash script replacements  If not  learn some more Perl   it is absolutely fantastic for that  If  on the other hand  you want a language that will grow with you as you want to do more  may I suggest Python or Ruby   Either way  good luck

User · Answer

Adding to previous answers  check the pexpect module for dealing with interactive commands  adduser  passwd etc

User · Answer

Yes  of course     Take a look at these libraries which help you Never write shell scripts again  Plumbum s motto     Plumbum  Sarge sh   Also  if you want to replace awk  sed and grep with something Python based then I recommend pyp -      The Pyed Piper   or pyp  is a linux command line text manipulation   tool similar to awk or sed  but which uses standard python string and   list methods as well as custom functions evolved to generate fast   results in an intense production environment

User · Answer

I just discovered how to combine the best parts of bash and ipython  Up to now this seems more comfortable to me than using subprocess and so on  You can easily copy big parts of existing bash scripts and e g  add error handling in the python way    And here is my result      usr bin env ipython3        How to have the most comfort scripting experience of your life                                                                                      by using ipython for scripting combined with subcommands from bash      1  echo     usr bin env ipython3   gt  scriptname ipy      creates new ipy-file     2  chmod  x scriptname ipy                              make in executable     3  starting with line 2  write normal python or do some of      the   magic of ipython  so that you can use unix commands      within python and even assign their output to a variable via      var    cmd1   cmd2   cmd3                            enjoy        4  run via   scriptname ipy - if it fails with recognizing   and        but parses raw python fine  please check again for the  ipy suffix    ugly example  please go and find more in the wild files    ls       grep  y  for file in files     echo  file   grep  p    sorry for this nonsense example      See IPython docs on system shell commands and using it as a system shell

User · Answer

In the beginning there was sh  sed  and awk  and find  and grep  and      It was good  But awk can be an odd little beast and hard to remember if you don t use it often  Then the great camel created Perl  Perl was a system administrator s dream  It was like shell scripting on steroids  Text processing  including regular expressions were just part of the language  Then it got ugly     People tried to make big applications with Perl  Now  don t get me wrong  Perl can be an application  but it can  can   look like a mess if you re not really careful  Then there is all this flat data business  It s enough to drive a programmer nuts   Enter Python  Ruby  et al  These are really very good general purpose languages  They support text processing  and do it well  though perhaps not as tightly entwined in the basic core of the language   But they also scale up very well  and still have nice looking code at the end of the day  They also have developed pretty hefty communities with plenty of libraries for most anything   Now  much of the negativeness towards Perl is a matter of opinion  and certainly some people can write very clean Perl  but with this many people complaining about it being too easy to create obfuscated code  you know some grain of truth is there  The question really becomes then  are you ever going to use this language for more than simple bash script replacements  If not  learn some more Perl   it is absolutely fantastic for that  If  on the other hand  you want a language that will grow with you as you want to do more  may I suggest Python or Ruby   Either way  good luck

User · Answer

pythonpy is a tool that provides easy access to many of the features from awk and sed  but using python syntax     echo me2   py -x  re sub  me    you   x   you2

User · Answer

I have published a package on PyPI  ez  Use pip install ez to install it   It has packed common commands in shell and nicely my lib uses basically the same syntax as shell   e g   cp source  destination  can handle both file and folder    wrapper of shutil copy shutil copytree and it decides when to use which one   Even more nicely  it can support vectorization like R   Another example  no os walk  use fls path  regex  to recursively find files and filter with regular expression and it returns a list of files with or without fullpath  Final example  you can combine them to write very simply scripts  files   fls      py     cp files  myDir   Definitely check it out   It has cost me hundreds of hours to write improve it

User · Answer

You can use python instead of bash with the ShellPy library    Here is an example that downloads avatar of Python user from Github   import json import os import tempfile    get the api answer with curl answer    curl https   api github com users python   syntactic sugar for checking returncode of executed process for zero if answer      answer json   json loads answer stdout      avatar url   answer json  avatar url        destination   os path join tempfile gettempdir     python png          execute curl once again  this time to get the image     result    curl  avatar url   gt   destination      if result            if there were no problems show the file         p ls -l  destination      else          print  Failed to download avatar        print  Avatar downloaded   else      print  Failed to access github api     As you can see  all expressions inside of grave accent       symbol are executed in shell  And in Python code  you can capture results of this execution and perform actions on it  For example   log    git log --pretty oneline --grep  Create    This line will first execute git log --pretty oneline --grep  Create  in shell and then assign the result to the log variable  The result has the following properties   stdout the whole text from stdout of the executed process  stderr the whole text from stderr of the executed process  returncode returncode of the execution  This is general overview of the library  more detailed description with examples can be found here

User · Answer

I suggest the awesome online book Dive Into Python   It s how I learned the language originally   Beyond teaching you the basic structure of the language  and a whole lot of useful data structures  it has a good chapter on file handling and subsequent chapters on regular expressions and more

User · Answer

I have published a package on PyPI  ez  Use pip install ez to install it   It has packed common commands in shell and nicely my lib uses basically the same syntax as shell   e g   cp source  destination  can handle both file and folder    wrapper of shutil copy shutil copytree and it decides when to use which one   Even more nicely  it can support vectorization like R   Another example  no os walk  use fls path  regex  to recursively find files and filter with regular expression and it returns a list of files with or without fullpath  Final example  you can combine them to write very simply scripts  files   fls      py     cp files  myDir   Definitely check it out   It has cost me hundreds of hours to write improve it

User · Answer

If your textfile manipulation usually is one-time  possibly done on the shell-prompt  you will not get anything better from python   On the other hand  if you usually have to do the same  or similar  task over and over  and you have to write your scripts for doing that  then python is great - and you can easily create your own libraries  you can do that with shell scripts too  but it s more cumbersome    A very simple example to get a feeling   import popen2 stdout text  stdin text popen2 popen2  your-shell-command-here   for line in stdout text    if line startswith           pass   else     jobID int line split      0  split   1  lstrip   lt    rstrip   gt           do something with jobID   Check also sys and getopt module  they are the first you will need

User · Answer

Any shell has several sets of features   The Essential Linux Unix commands   All of these are available through the subprocess library   This isn t always the best first choice for doing all external commands   Look also at shutil for some commands that are separate Linux commands  but you could probably implement directly in your Python scripts   Another huge batch of Linux commands are in the os library  you can do these more simply in Python  And -- bonus  -- more quickly   Each separate Linux command in the shell  with a few exceptions  forks a subprocess   By using Python shutil and os modules  you don t fork a subprocess   The shell environment features   This includes stuff that sets a command s environment  current directory and environment variables and what-not    You can easily manage this from Python directly   The shell programming features   This is all the process status code checking  the various logic commands  if  while  for  etc   the test command and all of it s relatives   The function definition stuff   This is all much  much easier in Python   This is one of the huge victories in getting rid of bash and doing it in Python   Interaction features   This includes command history and what-not   You don t need this for writing shell scripts   This is only for human interaction  and not for script-writing   The shell file management features   This includes redirection and pipelines   This is trickier   Much of this can be done with subprocess   But some things that are easy in the shell are unpleasant in Python   Specifically stuff like  a   b  c     something  gt result   This runs two processes in parallel  with output of a as input to b   followed by a third process   The output from that sequence is run in parallel with something and the output is collected into a file named result   That s just complex to express in any other language    Specific programs  awk  sed  grep  etc   can often be rewritten as Python modules   Don t go overboard   Replace what you need and evolve your  quot grep quot  module   Don t start out writing a Python module that replaces  quot grep quot   The best thing is that you can do this in steps   Replace AWK and PERL with Python   Leave everything else alone  Look at replacing GREP with Python   This can be a bit more complex  but your version of GREP can be tailored to your processing needs  Look at replacing FIND with Python loops that use os walk   This is a big win because you don t spawn as many processes  Look at replacing common shell logic  loops  decisions  etc   with Python scripts

User · Answer

Your best bet is a tool that is specifically geared towards your problem   If it s processing text files  then Sed  Awk and Perl are the top contenders   Python is a general-purpose dynamic language   As with any general purpose language  there s support for file-manipulation  but that isn t what it s core purpose is   I would consider Python or Ruby if I had a requirement for a dynamic language in particular   In short  learn Sed and Awk really well  plus all the other goodies that come with your flavour of  nix  All the Bash built-ins  grep  tr and so forth    If it s text file processing you re interested in  you re already using the right stuff

User · Answer

If you want to use Python as a shell  why not have a look at IPython   It is also good to learn interactively the language  If you do a lot of text manipulation  and if you use Vim as a text editor  you can also directly write plugins for Vim in python  just type   help python  in Vim and follow the instructions or have a look at this presentation  It is so easy and powerfull to write functions that you will use directly in your editor

User · Answer

Your best bet is a tool that is specifically geared towards your problem   If it s processing text files  then Sed  Awk and Perl are the top contenders   Python is a general-purpose dynamic language   As with any general purpose language  there s support for file-manipulation  but that isn t what it s core purpose is   I would consider Python or Ruby if I had a requirement for a dynamic language in particular   In short  learn Sed and Awk really well  plus all the other goodies that come with your flavour of  nix  All the Bash built-ins  grep  tr and so forth    If it s text file processing you re interested in  you re already using the right stuff

User · Answer

One reason I love Python is that it is much better standardized than the POSIX tools   I have to double and triple check that each bit is compatible with other operating systems   A program written on a Linux system might not work the same on a BSD system of OSX   With Python  I just have to check that the target system has a sufficiently modern version of Python   Even better  a program written in standard Python will even run on Windows

User · Answer

pythonpy is a tool that provides easy access to many of the features from awk and sed  but using python syntax     echo me2   py -x  re sub  me    you   x   you2

User · Answer

I suggest the awesome online book Dive Into Python   It s how I learned the language originally   Beyond teaching you the basic structure of the language  and a whole lot of useful data structures  it has a good chapter on file handling and subsequent chapters on regular expressions and more

User · Answer

I will give here my opinion based on experience   For shell    shell can very easily spawn read-only code  Write it and when you come back to it  you will never figure out what you did again  It s very easy to accomplish this  shell can do A LOT of text processing  splitting  etc in one line with pipes  it is the best glue language when it comes to integrate the call of programs in different programming languages    For python    if you want portability to windows included  use python  python can be better when you must manipulate just more than text  such as collections of numbers  For this  I recommend python    I usually choose bash for most of the things  but when I have something that must cross windows boundaries  I just use python

User · Answer

You can use python instead of bash with the ShellPy library    Here is an example that downloads avatar of Python user from Github   import json import os import tempfile    get the api answer with curl answer    curl https   api github com users python   syntactic sugar for checking returncode of executed process for zero if answer      answer json   json loads answer stdout      avatar url   answer json  avatar url        destination   os path join tempfile gettempdir     python png          execute curl once again  this time to get the image     result    curl  avatar url   gt   destination      if result            if there were no problems show the file         p ls -l  destination      else          print  Failed to download avatar        print  Avatar downloaded   else      print  Failed to access github api     As you can see  all expressions inside of grave accent       symbol are executed in shell  And in Python code  you can capture results of this execution and perform actions on it  For example   log    git log --pretty oneline --grep  Create    This line will first execute git log --pretty oneline --grep  Create  in shell and then assign the result to the log variable  The result has the following properties   stdout the whole text from stdout of the executed process  stderr the whole text from stderr of the executed process  returncode returncode of the execution  This is general overview of the library  more detailed description with examples can be found here

User · Answer

While researching this topic  I found this proof-of-concept code  via a comment at http   jlebar com 2010 2 1 Replacing Bash html  that lets you  write shell-like pipelines in Python using a terse syntax  and leveraging existing system tools where they make sense    for line in sh  cat  tmp junk2     cut d     f 1     sort    uniq      sys stdout write line

User · Answer

I suggest the awesome online book Dive Into Python   It s how I learned the language originally   Beyond teaching you the basic structure of the language  and a whole lot of useful data structures  it has a good chapter on file handling and subsequent chapters on regular expressions and more

User · Answer

I have built semi-long shell scripts  300-500 lines  and Python code which does similar functionality   When many external commands are being executed  I find the shell is easier to use   Perl is also a good option when there is lots of text manipulation

User · Answer

In the beginning there was sh  sed  and awk  and find  and grep  and      It was good  But awk can be an odd little beast and hard to remember if you don t use it often  Then the great camel created Perl  Perl was a system administrator s dream  It was like shell scripting on steroids  Text processing  including regular expressions were just part of the language  Then it got ugly     People tried to make big applications with Perl  Now  don t get me wrong  Perl can be an application  but it can  can   look like a mess if you re not really careful  Then there is all this flat data business  It s enough to drive a programmer nuts   Enter Python  Ruby  et al  These are really very good general purpose languages  They support text processing  and do it well  though perhaps not as tightly entwined in the basic core of the language   But they also scale up very well  and still have nice looking code at the end of the day  They also have developed pretty hefty communities with plenty of libraries for most anything   Now  much of the negativeness towards Perl is a matter of opinion  and certainly some people can write very clean Perl  but with this many people complaining about it being too easy to create obfuscated code  you know some grain of truth is there  The question really becomes then  are you ever going to use this language for more than simple bash script replacements  If not  learn some more Perl   it is absolutely fantastic for that  If  on the other hand  you want a language that will grow with you as you want to do more  may I suggest Python or Ruby   Either way  good luck

User · Answer

If your textfile manipulation usually is one-time  possibly done on the shell-prompt  you will not get anything better from python   On the other hand  if you usually have to do the same  or similar  task over and over  and you have to write your scripts for doing that  then python is great - and you can easily create your own libraries  you can do that with shell scripts too  but it s more cumbersome    A very simple example to get a feeling   import popen2 stdout text  stdin text popen2 popen2  your-shell-command-here   for line in stdout text    if line startswith           pass   else     jobID int line split      0  split   1  lstrip   lt    rstrip   gt           do something with jobID   Check also sys and getopt module  they are the first you will need

User · Answer

One reason I love Python is that it is much better standardized than the POSIX tools   I have to double and triple check that each bit is compatible with other operating systems   A program written on a Linux system might not work the same on a BSD system of OSX   With Python  I just have to check that the target system has a sufficiently modern version of Python   Even better  a program written in standard Python will even run on Windows

User · Answer

Adding to previous answers  check the pexpect module for dealing with interactive commands  adduser  passwd etc

User · Answer

In the beginning there was sh  sed  and awk  and find  and grep  and      It was good  But awk can be an odd little beast and hard to remember if you don t use it often  Then the great camel created Perl  Perl was a system administrator s dream  It was like shell scripting on steroids  Text processing  including regular expressions were just part of the language  Then it got ugly     People tried to make big applications with Perl  Now  don t get me wrong  Perl can be an application  but it can  can   look like a mess if you re not really careful  Then there is all this flat data business  It s enough to drive a programmer nuts   Enter Python  Ruby  et al  These are really very good general purpose languages  They support text processing  and do it well  though perhaps not as tightly entwined in the basic core of the language   But they also scale up very well  and still have nice looking code at the end of the day  They also have developed pretty hefty communities with plenty of libraries for most anything   Now  much of the negativeness towards Perl is a matter of opinion  and certainly some people can write very clean Perl  but with this many people complaining about it being too easy to create obfuscated code  you know some grain of truth is there  The question really becomes then  are you ever going to use this language for more than simple bash script replacements  If not  learn some more Perl   it is absolutely fantastic for that  If  on the other hand  you want a language that will grow with you as you want to do more  may I suggest Python or Ruby   Either way  good luck

User · Answer

Adding to previous answers  check the pexpect module for dealing with interactive commands  adduser  passwd etc

User · Answer

Your best bet is a tool that is specifically geared towards your problem   If it s processing text files  then Sed  Awk and Perl are the top contenders   Python is a general-purpose dynamic language   As with any general purpose language  there s support for file-manipulation  but that isn t what it s core purpose is   I would consider Python or Ruby if I had a requirement for a dynamic language in particular   In short  learn Sed and Awk really well  plus all the other goodies that come with your flavour of  nix  All the Bash built-ins  grep  tr and so forth    If it s text file processing you re interested in  you re already using the right stuff

User · Answer

Any shell has several sets of features   The Essential Linux Unix commands   All of these are available through the subprocess library   This isn t always the best first choice for doing all external commands   Look also at shutil for some commands that are separate Linux commands  but you could probably implement directly in your Python scripts   Another huge batch of Linux commands are in the os library  you can do these more simply in Python  And -- bonus  -- more quickly   Each separate Linux command in the shell  with a few exceptions  forks a subprocess   By using Python shutil and os modules  you don t fork a subprocess   The shell environment features   This includes stuff that sets a command s environment  current directory and environment variables and what-not    You can easily manage this from Python directly   The shell programming features   This is all the process status code checking  the various logic commands  if  while  for  etc   the test command and all of it s relatives   The function definition stuff   This is all much  much easier in Python   This is one of the huge victories in getting rid of bash and doing it in Python   Interaction features   This includes command history and what-not   You don t need this for writing shell scripts   This is only for human interaction  and not for script-writing   The shell file management features   This includes redirection and pipelines   This is trickier   Much of this can be done with subprocess   But some things that are easy in the shell are unpleasant in Python   Specifically stuff like  a   b  c     something  gt result   This runs two processes in parallel  with output of a as input to b   followed by a third process   The output from that sequence is run in parallel with something and the output is collected into a file named result   That s just complex to express in any other language    Specific programs  awk  sed  grep  etc   can often be rewritten as Python modules   Don t go overboard   Replace what you need and evolve your  quot grep quot  module   Don t start out writing a Python module that replaces  quot grep quot   The best thing is that you can do this in steps   Replace AWK and PERL with Python   Leave everything else alone  Look at replacing GREP with Python   This can be a bit more complex  but your version of GREP can be tailored to your processing needs  Look at replacing FIND with Python loops that use os walk   This is a big win because you don t spawn as many processes  Look at replacing common shell logic  loops  decisions  etc   with Python scripts

User · Answer

As of 2015 and Python 3 4 s release  there s now a reasonably complete user-interactive shell available at  http   xon sh  or https   github com scopatz xonsh  The demonstration video does not show pipes being used  but they ARE supported when in the default shell mode   Xonsh   conch   tries very hard to emulate bash  so things you ve already gained muscle memory for  like   env   uniq   sort -r   grep PATH   or   my-web-server 2 gt  amp 1   my-log-sorter   will still work fine   The tutorial is quite lengthy and seems to cover a significant amount of the functionality someone would generally expect at a ash or bash prompt    Compiles  Evaluates   amp  Executes  Command History and Tab Completion Help  amp  Superhelp with    amp     Aliases  amp  Customized Prompts Executes Commands and or   xsh Scripts which can also be imported Environment Variables including Lookup with     Input Output Redirection and Combining Background Jobs  amp  Job Control Nesting Subprocesses  Pipes  and Coprocesses Subprocess-mode when a command exists  Python-mode otherwise Captured Subprocess with      Uncaptured Subprocess with      Python Evaluation with     Filename Globbing with   or Regular Expression Filename Globbing with Backticks

User · Answer

I have built semi-long shell scripts  300-500 lines  and Python code which does similar functionality   When many external commands are being executed  I find the shell is easier to use   Perl is also a good option when there is lots of text manipulation

User · Answer

Adding to previous answers  check the pexpect module for dealing with interactive commands  adduser  passwd etc

User · Answer

If you want to use Python as a shell  why not have a look at IPython   It is also good to learn interactively the language  If you do a lot of text manipulation  and if you use Vim as a text editor  you can also directly write plugins for Vim in python  just type   help python  in Vim and follow the instructions or have a look at this presentation  It is so easy and powerfull to write functions that you will use directly in your editor

User · Answer

Your best bet is a tool that is specifically geared towards your problem   If it s processing text files  then Sed  Awk and Perl are the top contenders   Python is a general-purpose dynamic language   As with any general purpose language  there s support for file-manipulation  but that isn t what it s core purpose is   I would consider Python or Ruby if I had a requirement for a dynamic language in particular   In short  learn Sed and Awk really well  plus all the other goodies that come with your flavour of  nix  All the Bash built-ins  grep  tr and so forth    If it s text file processing you re interested in  you re already using the right stuff

User · Answer

I will give here my opinion based on experience   For shell    shell can very easily spawn read-only code  Write it and when you come back to it  you will never figure out what you did again  It s very easy to accomplish this  shell can do A LOT of text processing  splitting  etc in one line with pipes  it is the best glue language when it comes to integrate the call of programs in different programming languages    For python    if you want portability to windows included  use python  python can be better when you must manipulate just more than text  such as collections of numbers  For this  I recommend python    I usually choose bash for most of the things  but when I have something that must cross windows boundaries  I just use python

User · Answer

Yes  of course     Take a look at these libraries which help you Never write shell scripts again  Plumbum s motto     Plumbum  Sarge sh   Also  if you want to replace awk  sed and grep with something Python based then I recommend pyp -      The Pyed Piper   or pyp  is a linux command line text manipulation   tool similar to awk or sed  but which uses standard python string and   list methods as well as custom functions evolved to generate fast   results in an intense production environment

User · Answer

Any shell has several sets of features   The Essential Linux Unix commands   All of these are available through the subprocess library   This isn t always the best first choice for doing all external commands   Look also at shutil for some commands that are separate Linux commands  but you could probably implement directly in your Python scripts   Another huge batch of Linux commands are in the os library  you can do these more simply in Python  And -- bonus  -- more quickly   Each separate Linux command in the shell  with a few exceptions  forks a subprocess   By using Python shutil and os modules  you don t fork a subprocess   The shell environment features   This includes stuff that sets a command s environment  current directory and environment variables and what-not    You can easily manage this from Python directly   The shell programming features   This is all the process status code checking  the various logic commands  if  while  for  etc   the test command and all of it s relatives   The function definition stuff   This is all much  much easier in Python   This is one of the huge victories in getting rid of bash and doing it in Python   Interaction features   This includes command history and what-not   You don t need this for writing shell scripts   This is only for human interaction  and not for script-writing   The shell file management features   This includes redirection and pipelines   This is trickier   Much of this can be done with subprocess   But some things that are easy in the shell are unpleasant in Python   Specifically stuff like  a   b  c     something  gt result   This runs two processes in parallel  with output of a as input to b   followed by a third process   The output from that sequence is run in parallel with something and the output is collected into a file named result   That s just complex to express in any other language    Specific programs  awk  sed  grep  etc   can often be rewritten as Python modules   Don t go overboard   Replace what you need and evolve your  quot grep quot  module   Don t start out writing a Python module that replaces  quot grep quot   The best thing is that you can do this in steps   Replace AWK and PERL with Python   Leave everything else alone  Look at replacing GREP with Python   This can be a bit more complex  but your version of GREP can be tailored to your processing needs  Look at replacing FIND with Python loops that use os walk   This is a big win because you don t spawn as many processes  Look at replacing common shell logic  loops  decisions  etc   with Python scripts

User · Answer

I have built semi-long shell scripts  300-500 lines  and Python code which does similar functionality   When many external commands are being executed  I find the shell is easier to use   Perl is also a good option when there is lots of text manipulation

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If your textfile manipulation usually is one-time  possibly done on the shell-prompt  you will not get anything better from python   On the other hand  if you usually have to do the same  or similar  task over and over  and you have to write your scripts for doing that  then python is great - and you can easily create your own libraries  you can do that with shell scripts too  but it s more cumbersome    A very simple example to get a feeling   import popen2 stdout text  stdin text popen2 popen2  your-shell-command-here   for line in stdout text    if line startswith           pass   else     jobID int line split      0  split   1  lstrip   lt    rstrip   gt           do something with jobID   Check also sys and getopt module  they are the first you will need

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Any shell has several sets of features   The Essential Linux Unix commands   All of these are available through the subprocess library   This isn t always the best first choice for doing all external commands   Look also at shutil for some commands that are separate Linux commands  but you could probably implement directly in your Python scripts   Another huge batch of Linux commands are in the os library  you can do these more simply in Python  And -- bonus  -- more quickly   Each separate Linux command in the shell  with a few exceptions  forks a subprocess   By using Python shutil and os modules  you don t fork a subprocess   The shell environment features   This includes stuff that sets a command s environment  current directory and environment variables and what-not    You can easily manage this from Python directly   The shell programming features   This is all the process status code checking  the various logic commands  if  while  for  etc   the test command and all of it s relatives   The function definition stuff   This is all much  much easier in Python   This is one of the huge victories in getting rid of bash and doing it in Python   Interaction features   This includes command history and what-not   You don t need this for writing shell scripts   This is only for human interaction  and not for script-writing   The shell file management features   This includes redirection and pipelines   This is trickier   Much of this can be done with subprocess   But some things that are easy in the shell are unpleasant in Python   Specifically stuff like  a   b  c     something  gt result   This runs two processes in parallel  with output of a as input to b   followed by a third process   The output from that sequence is run in parallel with something and the output is collected into a file named result   That s just complex to express in any other language    Specific programs  awk  sed  grep  etc   can often be rewritten as Python modules   Don t go overboard   Replace what you need and evolve your  quot grep quot  module   Don t start out writing a Python module that replaces  quot grep quot   The best thing is that you can do this in steps   Replace AWK and PERL with Python   Leave everything else alone  Look at replacing GREP with Python   This can be a bit more complex  but your version of GREP can be tailored to your processing needs  Look at replacing FIND with Python loops that use os walk   This is a big win because you don t spawn as many processes  Look at replacing common shell logic  loops  decisions  etc   with Python scripts

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While researching this topic  I found this proof-of-concept code  via a comment at http   jlebar com 2010 2 1 Replacing Bash html  that lets you  write shell-like pipelines in Python using a terse syntax  and leveraging existing system tools where they make sense    for line in sh  cat  tmp junk2     cut d     f 1     sort    uniq      sys stdout write line

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As of 2015 and Python 3 4 s release  there s now a reasonably complete user-interactive shell available at  http   xon sh  or https   github com scopatz xonsh  The demonstration video does not show pipes being used  but they ARE supported when in the default shell mode   Xonsh   conch   tries very hard to emulate bash  so things you ve already gained muscle memory for  like   env   uniq   sort -r   grep PATH   or   my-web-server 2 gt  amp 1   my-log-sorter   will still work fine   The tutorial is quite lengthy and seems to cover a significant amount of the functionality someone would generally expect at a ash or bash prompt    Compiles  Evaluates   amp  Executes  Command History and Tab Completion Help  amp  Superhelp with    amp     Aliases  amp  Customized Prompts Executes Commands and or   xsh Scripts which can also be imported Environment Variables including Lookup with     Input Output Redirection and Combining Background Jobs  amp  Job Control Nesting Subprocesses  Pipes  and Coprocesses Subprocess-mode when a command exists  Python-mode otherwise Captured Subprocess with      Uncaptured Subprocess with      Python Evaluation with     Filename Globbing with   or Regular Expression Filename Globbing with Backticks

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If you want to use Python as a shell  why not have a look at IPython   It is also good to learn interactively the language  If you do a lot of text manipulation  and if you use Vim as a text editor  you can also directly write plugins for Vim in python  just type   help python  in Vim and follow the instructions or have a look at this presentation  It is so easy and powerfull to write functions that you will use directly in your editor

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I have built semi-long shell scripts  300-500 lines  and Python code which does similar functionality   When many external commands are being executed  I find the shell is easier to use   Perl is also a good option when there is lots of text manipulation

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