Use:

pip install -r <(pip freeze) --upgrade

在我看来，这个选项更简单易懂：

pip install -U `pip list --outdated | awk 'NR>2 {print $1}'`

解释是，pip-list——过时输出所有过时包的列表，格式如下：

Package   Version Latest Type 
--------- ------- ------ -----
fonttools 3.31.0  3.32.0 wheel
urllib3   1.24    1.24.1 wheel
requests  2.20.0  2.20.1 wheel

在awk命令中，NR>2跳过前两条记录（行），｛print$1｝选择每行的第一个单词（正如SergioAraujo所建议的，我删除了tail-n+3，因为awk确实可以处理跳过记录）。

使用virtualenv时，如果您只想升级添加到virtualenv的软件包，您可能需要执行以下操作：

pip install `pip freeze -l | cut --fields=1 -d = -` --upgrade

以下Windows cmd代码段执行以下操作：

将pip升级到最新版本。升级所有过时的软件包。对于正在升级的每个包，检查requirements.txt中的任何版本说明符。

@echo off
Setlocal EnableDelayedExpansion
rem https://stackoverflow.com/questions/2720014/

echo Upgrading pip...
python -m pip install --upgrade pip
echo.

echo Upgrading packages...
set upgrade_count=0
pip list --outdated > pip-upgrade-outdated.txt
for /F "skip=2 tokens=1,3 delims= " %%i in (pip-upgrade-outdated.txt) do (
    echo ^>%%i
    set package=%%i
    set latest=%%j
    set requirements=!package!

    rem for each outdated package check for any version requirements:
    set dotest=1
    for /F %%r in (.\python\requirements.txt) do (
        if !dotest!==1 (
            call :substr "%%r" !package! _substr
            rem check if a given line refers to a package we are about to upgrade:
            if "%%r" NEQ !_substr! (
                rem check if the line contains more than just a package name:
                if "%%r" NEQ "!package!" (
                    rem set requirements to the contents of the line:
                    echo requirements: %%r, latest: !latest!
                    set requirements=%%r
                )
                rem stop testing after the first instance found,
                rem prevents from mistakenly matching "py" with "pylint", "numpy" etc.
                rem requirements.txt must be structured with shorter names going first
                set dotest=0
            )
        )
    )
    rem pip install !requirements!
    pip install --upgrade !requirements!
    set /a "upgrade_count+=1"
    echo.
)

if !upgrade_count!==0 (
    echo All packages are up to date.
) else (
    type pip-upgrade-outdated.txt
)

if "%1" neq "-silent" (
    echo.
    set /p temp="> Press Enter to exit..."
)
exit /b


:substr
rem string substition done in a separate subroutine -
rem allows expand both variables in the substring syntax.
rem replaces str_search with an empty string.
rem returns the result in the 3rd parameter, passed by reference from the caller.
set str_source=%1
set str_search=%2
set str_result=!str_source:%str_search%=!
set "%~3=!str_result!"
rem echo !str_source!, !str_search!, !str_result!
exit /b

下面是用Python编写脚本的另一种方法：

import pip, tempfile, contextlib

with tempfile.TemporaryFile('w+') as temp:
    with contextlib.redirect_stdout(temp):
        pip.main(['list', '-o'])
    temp.seek(0)
    for line in temp:
        pk = line.split()[0]
        print('--> updating', pk, '<--')
        pip.main(['install', '-U', pk])

我最近一直在用pur。这很简单，切中要害。它会更新您的requirements.txt文件以反映升级，然后您可以像往常一样使用requirements.txt文件进行升级。

$ pip install pur
...
Successfully installed pur-4.0.1

$ pur
Updated boto3: 1.4.2 -> 1.4.4
Updated Django: 1.10.4 -> 1.10.5
Updated django-bootstrap3: 7.1.0 -> 8.1.0
All requirements up-to-date.

$ pip install --upgrade -r requirements.txt
Successfully installed Django-1.10.5 ...