Pip creates build/ directories
pip, python, virtualenv
Solution
The `build` directory is where a packages gets unpacked into and build from. When the package is installed successfully, pip removes the unpacked dir from `build`, unless you've removed `pip-delete-this-directory.txt`. As described in `pip-delete-this-directory.txt`:
This file is placed here by pip to indicate the source was put
here by pip.
Once this package is successfully installed this source code will be
deleted (unless you remove this file).
Thus its less important for runtime environment. You could ignore it safely.
Also, you could use `pip install -b customized_build_directory` to specify another directory as `build` base directory, for example `/tmp`
Furthermore, you could `pip install --no-download package_name` to rebuild the package w/o downloading it, if the previous installation of the package failed.
Problem
I use virtualenv to create isolated environments for my Python projects. Then i install dependencies with pip - Python package manager. Sometimes i forget to do `source venv/bin/activate`, and then pip creates `build/` directories inside my projects. Why does pip create them? May i delete them, and if not, may i put them in my `.hgignore` file? As far as i understand, pip stores source of downloaded packages there along a file called `pip-delete-this-directory.txt`. But when i delete it, everything still works, as the real code is being put into `venv/lib/python2.7/site-packages/`. Then what is `build/` really for?