How can I upgrade specific packages using pip and a requirements file?

I'm using pip with a requirements file, in a virtualenv, for my Django projects. I'm trying to upgrade some packages, notably Django itself, and I'm getting an error about source code conflicts:

Source in <virtualenv>/build/Django has version 1.2.3 that conflicts with Django==1.2.4 (from -r requirements/apps.txt (line 3))

That's after updating the version number of Django from 1.2.3 to 1.2.4 in my requirements file. I'm using this command to actually do the upgrade:

pip --install --upgrade -E `<virtualenv dir`> --requirement `<requirements file`>

I can't find any flag that triggers a total package re-download. I even tried running an uninstall command first, and then the install, but no dice. Am I missing something?

I ran the following command and it upgraded from 1.2.3 to 1.4.0

pip install Django --upgrade

Shortcut for upgrade:

pip install Django -U

Note: if the package you are upgrading has any requirements this command will additionally upgrade all the requirements to the latest versions available. In recent versions of pip, you can prevent this behavior by specifying --upgrade-strategy only-if-needed. With that flag, dependencies will not be upgraded unless the installed versions of the dependent packages no longer satisfy the requirements of the upgraded package.

First make sure you have checked the most voted answer.

I'm not sure if it's exactly your problem, but in my case, I wasn't able to upgrade Django to 1.2.4 - I was always finishing with 1.2.3 version, so I uninstalled Django with:

<virtualenv>/bin/pip uninstall Django

Then I removed <virtualenv>/build/Django directory and finally I installed the proper version with:

<virtualenv>/bin/pip install Django

According to pip documentation example 3:

pip install --upgrade django

But based on my experience, using this method will also upgrade any package related to it. Example:

Assume you want to upgrade somepackage that require Django >= 1.2.4 using this kind of method it will also upgrade somepackage and django to the newest update. Just to be safe, do:

# Assume you want to keep Django 1.2.4
pip install --upgrade somepackage django==1.2.4

Doing this will upgrade somepackage and keeping Django to the 1.2.4 version.

The shortcut command for --upgrade:

pip install Django --upgrade

Is:

pip install Django -U

If you only want to upgrade one specific package called somepackage, the command you should use in recent versions of pip is

pip install --upgrade --upgrade-strategy only-if-needed somepackage

This is very useful when you develop an application in Django that currently will only work with a specific version of Django (say Django=1.9.x) and want to upgrade some dependent package with a bug-fix/new feature and the upgraded package depends on Django (but it works with, say, any version of Django after 1.5).

The default behavior of pip install --upgrade django-some-package would be to upgrade Django to the latest version available which could otherwise break your application, though with the --upgrade-strategy only-if-needed dependent packages will now only be upgraded as necessary.