how to use subprocess to run a virtualenv package install

Question

I am writing a bootstrap code for one of my programs, and trying to install to my virtualenv directory using subprocess.call

initially I used :

subprocess.call(['pip', 'install', '-E', dir_name, 'processing'])

When re-running on ubuntu I noticed that the -E was outdated (http://pypi.python.org/pypi/pip/) and need to use:

virtualenv dir_name && dir_name/bin/pip install processing

This works fine from the cmd line but will not work in subprocess:

subprocess.call(['virtualenv', dir_name, '&&', '{0}/bin/pip'.format(dir_name), 'install', 'processing'])

Returns this error message:

There must be only one argument: DEST_DIR (you gave dir_name && dir_name/bin/pip install processing)
Usage: virtualenv [OPTIONS] DEST_DIR

I have also tried virtualenv.create_bootstrap_script(extra_text) (but can not figure it out and have some additional scripts I am running that are from git)

Wondering what I am doing wrong in subprocess or what I can change.

Thanks!

Answer 1

Just check the status of the first command, then conditionally run the second:

retval = subprocess.call(
 ['virtualenv', dir_name]
)
if retval == 0:
 # a 0 return code indicates success
 retval = subprocess.call(
 ['{0}/bin/pip'.format(dir_name), 'install', 'processing']
 )
 if retval == 0:
 print "ERROR: Failed to install package 'processing'"
else:
 print "ERROR: Failed to created virtualenv properly."

Warning: danger below!

In order for the && token to work, you must use the argument shell=True in subprocess.call. However, you MUST NOT use shell=True if you're accepting input from the user, because it will then allow arbitrary code execution.

Additionally, you need to join the args together.

If you're using a dir_name that you are hard coding:

cmdline = ' '.join(['virtualenv', dir_name, '&&', '{0}/bin/pip'.format(dir_name), 'install', 'processing'])
subprocess.call(
 cmdline,
 shell=True
)

• gina turco: Thanks! subprocess.call(['{0}/bin/pip'.format(dir_name), 'install', 'processing']) works!
• gina turco: sorry I hit enter before i could type everything out and fix my edit