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pip list --outdated 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 pip-upgrade-outdated.txt
for /F "skip=2 tokens=1,3 delims= " %%i in (pip-upgrade-outdated.txt) do (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    rem for each outdated package check for any version requirements: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    type pip-upgrade-outdated.txt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

还没有内置标志。从pip版本22.3开始，--过时和--format=freeze变得互斥。使用Python解析json输出：

pip --disable-pip-version-check list --outdated --format=json | python -c "import json, sys; print('\n'.join([x['name'] for x in json.load(sys.stdin)]))"

如果您正在使用pip<22.3，则可以使用：

pip list --outdated --format=freeze | grep -v '^\-e' | cut -d = -f 1  | xargs -n1 pip install -U

对于旧版本的pip：

pip freeze --local | grep -v '^\-e' | cut -d = -f 1  | xargs -n1 pip install -U

grep是跳过可编辑（“-e”）包定义，正如@jawache所建议的那样。（是的，您可以用sed、awk、perl或…替换grep+cut）。xargs的-n1标志防止在更新一个包失败时停止所有操作（谢谢@andss）。

注意：这有无限的潜在变化。我试图让这个答案简短明了，但请在评论中提出建议！

拉玛纳的回答对我来说是最好的，但我不得不补充几点：

import pip
for dist in pip.get_installed_distributions():
    if 'site-packages' in dist.location:
        try:
            pip.call_subprocess(['pip', 'install', '-U', dist.key])
        except Exception, exc:
            print exc

站点包检查排除了我的开发包，因为它们不在系统站点包目录中。try-except只是跳过已从PyPI中删除的包。

对于endolith：我也希望有一个简单的pip.install（dist.key，upgrade=True），但它看起来不像是要让命令行以外的任何东西使用pip（文档没有提到内部API，pip开发人员也没有使用docstring）。

拉玛纳回答的一个线性版本。

python -c 'import pip, subprocess; [subprocess.call("pip install -U " + d.project_name, shell=1) for d in pip.get_installed_distributions()]'

Windows上最短、最简单的。

pip freeze > requirements.txt && pip install --upgrade -r requirements.txt && rm requirements.txt