PIP - the Package Installer for Python


pip : How to list the installed modules ?

pip list
module1 (x.y.z)
module2 (x.y.z)
module3 (x.y.z)
pip freeze
pip show getopt wstools
Name: wstools
Version: 0.4.3
Summary: wstools
Home-page: https://github.com/pycontribs/wstools.git
Author: Gregory Warnes, kiorky, sorin
Author-email: Gregory.R.Warnes@Pfizer.com, kiorky@cryptelium.net, sorin.sbarnea+os@gmail.com
License: UNKNOWN
Location: /usr/lib/python2.7/dist-packages
and finally :
Python 2.7.13 (default, Sep 26 2018, 18:42:22)
[GCC 6.3.0 20170516] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> help("modules")
Please wait a moment while I gather a list of all available modules...

BaseHTTPServer      argparse            ihooks              samba
Bastion             array               imaplib             sched
CDROM               ast                 imghdr              secretstorage
CGIHTTPServer       asynchat            imp                 select

What is PIP ?


pip3 : how to make an "offline install" ?

It is pretty common that servers aren't directly connected to the Internet, which makes it impractical to download + install packages with tools like pip3 or apt. The workaround is then to make an "offline install" :
  1. from a machine that has internet access, download the required packages and their dependencies :
    pip3 download ansible
    Collecting ansible
      Downloading https://files.pythonhosted.org/packages/e8/b2/c10b82573bb494d9e0764b5c75eb7be1e649082435280f2220976d1a3b33/ansible-2.9.11.tar.gz (14.2MB)
        100% |████████████████████████████████| 14.3MB 94kB/s
      Saved ./ansible-2.9.11.tar.gz
    Collecting PyYAML (from ansible)
      Downloading https://files.pythonhosted.org/packages/64/c2/b80047c7ac2478f9501676c988a5411ed5572f35d1beff9cae07d321512c/PyYAML-5.3.1.tar.gz (269kB)
        100% |████████████████████████████████| 276kB 1.1MB/s
      Saved ./PyYAML-5.3.1.tar.gz
    Collecting cryptography (from ansible)
      Downloading https://files.pythonhosted.org/packages/26/d6/e8b087b9ae062d737c67c3bf76e30333bda9295ca17205062e8ed2c872de/cryptography-3.0-cp35-abi3-manylinux1_x86_64.whl (2.7MB)
        100% |████████████████████████████████| 2.7MB 368kB/s
      Saved ./cryptography-3.0-cp35-abi3-manylinux1_x86_64.whl
    Collecting jinja2 (from ansible)
      Downloading https://files.pythonhosted.org/packages/30/9e/f663a2aa66a09d838042ae1a2c5659828bb9b41ea3a6efa20a20fd92b121/Jinja2-2.11.2-py2.py3-none-any.whl (125kB)
        100% |████████████████████████████████| 133kB 2.2MB/s
      Saved ./Jinja2-2.11.2-py2.py3-none-any.whl
    Collecting six>=1.4.1 (from cryptography->ansible)
      Downloading https://files.pythonhosted.org/packages/ee/ff/48bde5c0f013094d729fe4b0316ba2a24774b3ff1c52d924a8a4cb04078a/six-1.15.0-py2.py3-none-any.whl
      Saved ./six-1.15.0-py2.py3-none-any.whl
    Collecting cffi!=1.11.3,>=1.8 (from cryptography->ansible)
      Downloading https://files.pythonhosted.org/packages/d1/fd/10e2050b3afcb03d78b2b33212c3ff17b3985ae25d0feb34c0c9eb417549/cffi-1.14.1-cp37-cp37m-manylinux1_x86_64.whl (401kB)
        100% |████████████████████████████████| 409kB 1.1MB/s
      Saved ./cffi-1.14.1-cp37-cp37m-manylinux1_x86_64.whl
    Collecting MarkupSafe>=0.23 (from jinja2->ansible)
      Using cached https://files.pythonhosted.org/packages/98/7b/ff284bd8c80654e471b769062a9b43cc5d03e7a615048d96f4619df8d420/MarkupSafe-1.1.1-cp37-cp37m-manylinux1_x86_64.whl
      Saved ./MarkupSafe-1.1.1-cp37-cp37m-manylinux1_x86_64.whl
    Collecting pycparser (from cffi!=1.11.3,>=1.8->cryptography->ansible)
      Using cached https://files.pythonhosted.org/packages/ae/e7/d9c3a176ca4b02024debf82342dab36efadfc5776f9c8db077e8f6e71821/pycparser-2.20-py2.py3-none-any.whl
      Saved ./pycparser-2.20-py2.py3-none-any.whl
    Successfully downloaded ansible PyYAML cryptography jinja2 six cffi MarkupSafe pycparser
  2. send the downloaded files to the destination machine
  3. install packages locally :
    pip3 install path/to/downloadedPackage
    • PyYAML is a dependency of ansible and it looks like pip3 install ./ansible-2.9.11.tar.gz is not able to install PyYAML from the local package (tries to download it instead). In such case, install dependencies first, then retry installing the main package.
    • Looks like the downloaded packages (architecture, version, ... ?) match the machine they are downloaded from, but may not fit the destination machine and fail to install (to be investigated).

pip3 : error: invalid command 'bdist_wheel'


Full error message :
  Failed building wheel for ansible
  Running setup.py clean for ansible
  Running setup.py bdist_wheel for pycparser ... error
  Complete output from command /home/kevin/myGreatProject/myVirtualEnvironment/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-install-bz2ssx4w/pycparser/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /tmp/pip-wheel-0z6zygi4 --python-tag cp37:

  error: invalid command 'bdist_wheel'

I got this error while installing Ansible but it can occur during the installation of any package since something is missing locally .


  1. pip3 install wheel --upgrade
  2. retry the command you were running in the first place

pip3 : how to list all available versions of a package and install a specific version ?

When playing with packages and versions, it may be safe to work inside a virtual environment.

List all available version of a package (source) :

Looks like there is no tool or command flag to do so, and the only option is to ask the installation of a non-existent version to read the expected information from the error message :
pip3 install ansible==
Collecting ansible==
  Could not find a version that satisfies the requirement ansible== (from versions: 1.0, 1.1, 1.2, 1.2.1, 1.2.2, 1.2.3, 1.3.0, 1.3.1, 1.3.2, 1.3.3, 1.3.4, 1.4, 1.4.1, 1.4.2, 1.4.3, 1.4.4, 1.4.5, 1.5, 1.5.1, 1.5.2, 1.5.3, 1.5.4, 1.5.5, 1.6, 1.6.1, 1.6.2, 1.6.3, 1.6.4, 1.6.5, 1.6.6, 1.6.7, 1.6.8, 1.6.9, 1.6.10, 1.7, 1.7.1, 1.7.2, 1.8, 1.8.1, 1.8.2, 1.8.3, 1.8.4,, 1.9.1, 1.9.2, 1.9.3, 1.9.4, 1.9.5, 1.9.6,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2.5.0a1, 2.5.0b1, 2.5.0b2, 2.5.0rc1, 2.5.0rc2, 2.5.0rc3, 2.5.0, 2.5.1, 2.5.2, 2.5.3, 2.5.4, 2.5.5, 2.5.6, 2.5.7, 2.5.8, 2.5.9, 2.5.10, 2.5.11, 2.5.12, 2.5.13, 2.5.14, 2.5.15, 2.6.0a1, 2.6.0a2, 2.6.0rc1, 2.6.0rc2, 2.6.0rc3, 2.6.0rc4, 2.6.0rc5, 2.6.0, 2.6.1, 2.6.2, 2.6.3, 2.6.4, 2.6.5, 2.6.6, 2.6.7, 2.6.8, 2.6.9, 2.6.10, 2.6.11, 2.6.12, 2.6.13, 2.6.14, 2.6.15, 2.6.16, 2.6.17, 2.6.18, 2.6.19, 2.7.0.dev0, 2.7.0a1, 2.7.0b1, 2.7.0rc1, 2.7.0rc2, 2.7.0rc3, 2.7.0rc4, 2.7.0, 2.7.1, 2.7.2, 2.7.3, 2.7.4, 2.7.5, 2.7.6, 2.7.7, 2.7.8, 2.7.9, 2.7.10, 2.7.11, 2.7.12, 2.7.13, 2.8.0a1, 2.8.0b1, 2.8.0rc1, 2.8.0rc2, 2.8.0rc3, 2.8.0, 2.8.1, 2.8.2, 2.8.3, 2.8.4, 2.8.5, 2.9.0b1, 2.9.0rc1, 2.9.0rc2, 2.9.0rc3)
No matching distribution found for ansible==
Improved version :
pip3 install ansible== 2>&1 | tr '), ' '\n' | grep -E '^[0-9]' | sort -nr | less

Install a specific version :

From above :
pip3 install ansible==2.7.9

pip3 ends on error: command 'x86_64-linux-gnu-gcc' failed with exit status 1


While trying to setup Molecule, a pip3 install -U [packages] command ends on :
building 'psutil._psutil_linux' extension
creating build/temp.linux-x86_64-3.7
creating build/temp.linux-x86_64-3.7/psutil
x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -DPSUTIL_POSIX=1 -DPSUTIL_VERSION=563 -DPSUTIL_LINUX=1 -I/home/bob/virtualenvs/projectName/include -I/usr/include/python3.7m -c psutil/_psutil_common.c -o build/temp.linux-x86_64-3.7/psutil/_psutil_common.o
psutil/_psutil_common.c:9:10: fatal error: Python.h: No such file or directory	the line above the error 
 #include <Python.h>
compilation terminated.
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1			the error


As said here : Sometimes it's the line above this error you should look at. It should tell you what package is missing.


apt install python3-dev

Check :

dpkg -S Python.h
libpython3.7-dev:amd64: /usr/include/python3.7m/Python.h


Error after upgrading pip : ImportError: cannot import name 'main'


I don't have the exact sequence of events and commands that led me here, but what I read while fixing this emphasize that PEBKAC :
  1. while actually trying to use youtube-dl, it displayed my current version was out-of-date and I should upgrade (which I did)
  2. the upgrade process suggested to upgrade pip too, and even offered the command line to do so. I copy-pasted it and executed it ()
  3. after that, every youtube-dl command failed on :
    Traceback (most recent call last):
      File "/usr/local/bin/youtube-dl", line 6, in <module>
        from youtube_dl import main
    ImportError: cannot import name 'main'



This GitHub issue details the reasons of this error (the PEBKAC part, notably) and hints to debug / fix.

Unless explicitly specified, all commands below were run as a non-root user.
  1. First, identify the full absolute path of the executable script that you are running :
    which youtube-dl
  2. Once you have identified the script, make sure you can reproduce the problem using the absolute path to that script :
    Traceback (most recent call last):
      File "/usr/local/bin/youtube-dl", line 6, in <module>
        from youtube_dl import main
    ImportError: cannot import name 'main'
  3. work out which version of Python the script is using to run pip. You'll often be able to get that from the shebang line of the script :
    head /usr/local/bin/youtube-dl
  4. Once you know which Python is running pip, you can run python -m pip to invoke pip :
    python -m pip
    (returns the 'usage' page, but no error)
    python3 -m pip
      File "/usr/share/python-wheels/pkg_resources-0.0.0-py2.py3-none-any.whl/pkg_resources/__init__.py", line 639, in __init__
      File "/usr/share/python-wheels/pkg_resources-0.0.0-py2.py3-none-any.whl/pkg_resources/__init__.py", line 695, in add_entry
      File "/usr/share/python-wheels/pkg_resources-0.0.0-py2.py3-none-any.whl/pkg_resources/__init__.py", line 2012, in find_on_path
    PermissionError: [Errno 13] Permission denied: '/usr/local/lib/python3.5/dist-packages/youtube_dl-2019.3.18.dist-info'
    The last line is quite surprising and also recalls something seen minutes ago. The permissions were actually kinda weird :
  5. as root :
    ll /usr/local/lib/python3.5/dist-packages
    drwx--S--- 6 root staff 4.0K Mar 19 08:52 youtube_dl
    drwx--S--- 2 root staff 4.0K Mar 19 08:52 youtube_dl-2019.3.18.dist-info
  6. as root again :
    chmod -R a+rX /usr/local/lib/python3.5/dist-packages/
  7. then, as non-root :
    (the 'usage' page )

This is highly context-specific and not exactly a "clean" solution, but maybe this will give you hints to find the root cause on your side... If anything, this issue,at least, led me to some best practices :

Best practices (source) :

First, some general advice. It is assumed that anyone encountering issues will have failed to follow some part of this advice. Listing these items here is not intended to imply that "it's your fault and we won't help", but rather to help users to identify what went wrong, so that they can work out what to do next more easily.

  1. Only ever use your system package manager to upgrade the system pip. The system installed pip is owned by the distribution, and if you don't use distribution-supplied tools to manage it, you will hit problems. Yes, we know pip says "you should upgrade with pip install -U pip" - that's true in a pip-managed installation, ideally distributions should patch this message to give appropriate instructions in the system pip, but they don't. We're working with them on this, but it's not going to happen soon (remember, we're looking at cases where people are upgrading old versions of pip here, so patches to new versions won't help).
  2. Never use sudo with pip. This follows on from the first point. If you think you need to use sudo, you're probably trying to modify a distribution-owned file. See point 1.
  3. Prefer to use --user. By doing this, you only ever install packages in your personal directories, and so you avoid interfering with the system copy of pip. But there are PATH issues you need to be aware of here. We'll cover these later. Put simply, it's possible to follow this advice, and still hit problems, because you're not actually running the wrapper you installed as --user.

pip ends on error TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'


While trying to install mps-youtube (sudo pip3 install mps-youtube), I get the error :
MANY lines describing the exceptions
TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'


This is because the installed version of pip (probably from the Debian packages) is too old.


  1. apt remove python-pip python3-pip
  2. proxyString="Kevin:p4ssw0rd@proxy:3128"; export http_proxy="http://$proxyString"; export https_proxy="https://$proxyString"
  3. cd /tmp && wget https://bootstrap.pypa.io/get-pip.py
  4. python get-pip.py
    Collecting pip
      Downloading pip-9.0.1-py2.py3-none-any.whl (1.3MB)
        100% |████████████████████████████████| 1.3MB 781kB/s
    Installing collected packages: pip
    Successfully installed pip-9.0.1
  5. python3 get-pip.py
    Collecting pip
      Using cached pip-9.0.1-py2.py3-none-any.whl
    Collecting wheel
      Downloading wheel-0.30.0-py2.py3-none-any.whl (49kB)
        100% |████████████████████████████████| 51kB 718kB/s
    Installing collected packages: pip, wheel
    Successfully installed pip-9.0.1 wheel-0.30.0
  6. You can now retry installing :
    /usr/local/bin/pip3 install mps-youtube
    Collecting mps-youtube
      Downloading mps_youtube- (74kB)
        100% |████████████████████████████████| 81kB 974kB/s
    Requirement already satisfied: pafy!=0.4.0,!=0.4.1,!=0.4.2,>=0.3.82 in /usr/lib/python3/dist-packages (from mps-youtube)
    Installing collected packages: mps-youtube
    Successfully installed mps-youtube-

How to install packages for Python3 with pip ?

apt install python3-pip; pip3 install requests