Activating a Python virtual environment from a script file
This guide explains how to activate a Python virtual environment directly from a script, allowing you to use modules installed in that environment. This is useful for scenarios like Python CGI scripts, which are executed directly by the web server.
Important Notes
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Activating the virtual environment in a script
To activate a virtual environment from a script, use the activate_this.py file located inside the virtual environment. This allows the script to access all installed modules without manually activating the environment in the shell.
Here’s an example Python CGI script:
#!/home/username/virtualenv/application/x.y/bin/python
import os
import sys
import pkg_resources
# Activate the virtual environment
activate_this = str(os.path.dirname(sys.executable)) + '/activate_this.py'
with open(activate_this) as f:
code = compile(f.read(), activate_this, 'exec')
exec(code, dict(__file__=activate_this))
# Import a module from the virtual environment
from module import variable
# Output HTML
print("Content-type:text/html\r\n\r\n")
print('<html>')
print('<head>')
print('<title>Virtualenv test</title>')
print('</head>')
print('<body>')
print('<h3>If you see this, the module import was successful</h3>')
print('Python version: ' + sys.version)
print('<br/>')
print('Python executable: ' + str(sys.executable))
print('<br/>')
print('Installed modules: ')
print([p.project_name for p in pkg_resources.working_set])
print('<br/>')
print('</body>')
print('</html>')How to use this script
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Replace the following placeholders in the script:
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username→ your hosting.com account username -
application→ the name of your Python application -
x.y→ Python version of the virtual environment (e.g., 2.7, 3.8) -
module→ a module installed in your virtual environment -
variable→ a variable or class from that module
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Save the script in your CGI-enabled directory (e.g.,
~/public_html/script.cgi). -
Run the script from the command line or load it in a web browser:
python ~/public_html/script.cgiExpected Output
If the script runs successfully, you should see a message like:
“If you see this, the module import was successful”
It also displays:
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Python version
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Path to the Python executable
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List of installed modules
If you do not see this message, check for syntax errors or missing modules and ensure the virtual environment path is correct.
