Can I use a single python script to create a virtualenv and install requirements.txt?

Question

I am trying to create a script where i create a virtualenv if it has not been made, and then install requirements.txt in it.

I can't call the normal source /env/bin/activate and activate it, then use pip to install requirements.txt. Is there a way to activate the virtualenv and then install my requirements from a single python script?

my code at the moment:

    if not os.path.exists(env_path):
        call(['virtualenv', env_path])

    else:
        print "INFO: %s exists." %(env_path)



    try:
        call(['source', os.path.join(env_path, 'bin', 'activate')])

    except Exception as e:
        print e

the error is "No such file directory"

Thanks

Answer 1

source is a shell builtin command, not a program. It cannot and shouldn't be executed with subprocess. You can activate your fresh virtual env by executing activate_this.py in the current process:

if not os.path.exists(env_path):
    call(['virtualenv', env_path])
    activate_this = os.path.join(env_path, 'bin', 'activate_this.py')
    execfile(activate_this, dict(__file__=activate_this))

else:
    print "INFO: %s exists." %(env_path)