Introduction to Python Programming
All the required Files
The Python Shell
#!/usr/bin/env python
import os
import re
import subprocess
import logging
import optparse
logging.basicConfig(level=logging.INFO,
format=’%(asctime)s %(levelname)s %(message)s’)
def main():
usage = “usage: %prog [options]”
parser = optparse.OptionParser(usage)
parser.add_option(“-m”, “–merge-master”, dest=”merge_master”,
action=”store_true”,
default=False,
help=”Merges the latest master into the current branch”)
parser.add_option(“-B”, “–merge-branch”, dest=”merge_branch”,
action=”store_true”,
default=False,
help=”Merge the current branch into master; forces -m”)
options, args = parser.parse_args()
if not options.merge_master and not options.merge_branch:
parser.error(‘Must choose one– try -m or -B’)
# Merging branch requires latest merged master
if options.merge_branch:
options.merge_master = True
if options.merge_master:
output,_ = call_command(‘git status’)
match = re.search(‘# On branch ([^\s]*)’, output)
branch = None
if match is None:
raise Exception(‘Could not get status’)
elif match.group(1) == ‘master’:
raise Exception(‘You must be in the branch that you want to merge, not master’)
else:
branch = match.group(1)
logging.info(‘In branch %s’ % branch)
if output.endswith(‘nothing to commit (working directory clean)\n’):
logging.info(‘Directory clean in branch: %s’ % branch)
else:
raise Exception(‘Directory not clean, must commit:\n%s’ % output)
logging.info(‘Switching to master branch’)
output,_ = call_command(‘git checkout master’)
output,_ = call_command(‘git pull’)
logging.info(‘Pulled latest changes from origin into master’)
logging.info(‘Ensuring master has the latest changes’)
output,_ = call_command(‘git pull’)
if ‘up-to-date’ not in output:
raise Exception(‘Local copy was not up to date:\n%s’ % output)
else:
logging.info(‘Local copy up to date’)
logging.info(‘Switching back to branch: %s’ % branch)
output,_ = call_command(‘git checkout %s’ % branch)
output,_ = call_command(‘git merge master’)
logging.info(‘Merged latest master changes into branch: %s’ % branch)
logging.info(‘Ensuring latest master changes in branch: %s’ % branch)
output,_ = call_command(‘git merge master’)
if ‘up-to-date’ not in output:
raise Exception(‘Branch %s not up to date:\n%s’ % (branch, output))
else:
logging.info(‘Branch %s up to date’ % branch)
logging.info(‘Successfully merged master into branch %s’ % branch)
if options.merge_branch:
logging.info(‘Switching to master branch’)
output,_ = call_command(‘git checkout master’)
output,_ = call_command(‘git merge %s’ % branch)
logging.info(‘Merged into master latest branch changes: %s’ % branch)
output,_ = call_command(‘git branch -d %s’ % branch)
logging.info(‘Deleted safely branch: %s’ % branch)
call_command(‘git push’)
logging.info(‘Pushed master up to origin’)
logging.info(‘Ensuring that origin has latest master’)
stdout,stderr = call_command(‘git push’)
if stderr == ‘Everything up-to-date\n’:
logging.info(‘Remote repository up to date: %s’ % branch)
else:
raise Exception(‘Remote repository not up to date:\n%s’ % output)
logging.info(‘Successfully merged branch %s into master and pushed to origin’ % branch )
def call_command(command):
process = subprocess.Popen(command.split(‘ ‘),
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
return process.communicate()
if __name__ == “__main__”:
main()
Summary
There is a possibility of extending the call command () function. This can be possibly done by piping output of the calls that had been made before. The extension of the call command facilitates the translation of the shell scripts to python (Hall & Stacey, 2009). In order to perform this function, the programmer ought to nest the functions into each other in reversed order. This will help in getting the functionality of the standard Linux pipe. In this case, the programmer ought to include the shlex modification. The following illustration backup the above python shell (Wu, 2010)
Code:
#!/usr/bin/env python
import subprocess, shlex
def call_command(command, pipe=None):
process = subprocess.Popen(shlex.split(command),
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
output=process.communicate(input=pipe)
return output
Example:
Shell:
ls | grep “pipe ftw”
Python:
call_command(“grep \”pipe ftw\””, pipe=call_command(“ls”)[0])
Reference
Hall, T. & Stacey, J. P. (2009). Python 3 for Absolute Beginners. New York: Apress.
Wu, C. (2010). Pro DLR in .NET 4. New York: Apress.
