pip forces re-installation of existing packets when used with --target option

[drasko]

Hi all,
I need to install some Python modules on external SD card, as I do not have space on my embedded device. That's why I use --target option of PIP.

However, it looks like --target implies --ignore-installed, so downloading and re-installation of already installed packages is performed.

In the case of embedded device this might be unacceptable - not only that this takes a lot of time and resources, but also packets on these devices are installed via special cross-compilation systems and should be mandatory kept in this state and version.

Example:

root@WEIO:/# pip freeze
PyYAML==3.8
futures==2.1.4
gevent==1.0
greenlet==0.4.0
pyserial==2.6
sockjs-tornado==1.0.0
tornado==3.0.1
wsgiref==0.1.2 

root@WEIO:/# pip install --target /weioUser/sd/pythonExtra --build /weioUser/sd/pythonExtra/build ouimeaux
Downloading/unpacking ouimeaux
  Downloading ouimeaux-0.7.3.tar.gz (506kB): 506kB downloaded
  Running setup.py egg_info for package ouimeaux

Downloading/unpacking gevent>=1.0 (from ouimeaux)
  Downloading gevent-1.0.1.tar.gz (1.5MB): 1.5MB downloaded
  Running setup.py egg_info for package gevent

Downloading/unpacking requests>=2.3.0 (from ouimeaux)
^CCleaning up...
Operation cancelled by user
Storing complete log in /root/.pip/pip.log
^C
root@WEIO:/# 

As you can see, although I have gevent==1.0 it is re-installed (unacceptable on OpenWrt where gevent is specially cross-compiled by OpenWrt build system). Package ouimeaux requirement is here: https://github.com/iancmcc/ouimeaux/blob/master/requirements.txt#L1, which shows that I already have a good version of gevent in my system.

BR,
Drasko

[piotr-dobrogost]

This is duplicate of #1818.

[dstufft]

Closing this it was a duplicate of #1818 which was fixed in pip 1.5.