As @sinoroc suggested correct way of installing a package via pip is using separate process since pip may cause closing a thread or may require a restart of interpreter to load new installed package so this is the right way of using the API: subprocess.check_call[[sys.executable, '-m', 'pip', 'install', 'SomeProject']] but since Python allows to access internal API and you know what you're using the API for you may want to use internal API anyway eg. if you're building own GUI package manager with alternative resourcess like
//www.lfd.uci.edu/~gohlke/pythonlibs/
Following soulution is OUT OF DATE, instead of downvoting suggest updates. see //github.com/pypa/pip/issues/7498 for reference.
UPDATE: Since pip version 10.x there is no more get_installed_distributions[] or main method
under import pip instead use import pip._internal as pip.
UPDATE ca. v.18 get_installed_distributions[] has been removed. Instead you may use generator freeze like this:
from pip._internal.operations.freeze import freeze
print[[package for package in freeze[]]]
# eg output ['pip==19.0.3']
If you want to use pip inside the Python interpreter, try this:
import pip
package_names=['selenium', 'requests'] #packages to install
pip.main[['install'] + package_names + ['--upgrade']]
# --upgrade to install or update existing packages
If you need to update every installed package, use following:
import pip
for i in pip.get_installed_distributions[]:
pip.main[['install', i.key, '--upgrade']]
If you want to stop installing other packages if any installation fails, use it in one single pip.main[[]] call:
import pip
package_names = [i.key for i in pip.get_installed_distributions[]]
pip.main[['install'] + package_names + ['--upgrade']]
Note: When you
install from list in file with -r / --requirement parameter you do NOT need open[] function.
pip.main[['install', '-r', 'filename']]
Warning: Some parameters as simple --help may cause python interpreter to stop.
Curiosity: By using pip.exe you actually use python interpreter and pip module anyway. If you unpack pip.exe or pip3.exe regardless it's python 2.x or 3.x, inside is the SAME single file __main__.py:
# -*- coding: utf-8 -*-
import re
import sys
from pip import main
if __name__ == '__main__':
sys.argv[0] = re.sub[r'[-script\.pyw?|\.exe]?$', '', sys.argv[0]]
sys.exit[main[]]
The pip package installer must be run from the command line. If you try to install a package from the Python interpreter or in a Python program, you’ll encounter the SyntaxError: invalid syntax error.
In this guide, we’re going to discuss the cause of the pip install invalid syntax error and what it means. We’ll walk through an example of this error so you can learn how to fix it in your code.
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pip install invalid syntax
Python pip is a package installer. The pip tool lets you download and install packages from the Python Package Index, where thousands of libraries are available with which you can work in your code.
The pip tool runs as its own command line interface. pip is
separate from your installation of Python. This is because pip is an installer rather than a tool that executes code.
If these tools were bundled together, it would be more confusing for developers who want to install packages because similar syntax used to start a Python program would also apply to installing modules.
This behavior is common across programming environments. Node.js relies on npm to install packages. To run a program using Node.js, you need to use the node command.
An Example Scenario
We’re going to set up the Beautiful Soup 4 library [bs4] in a development environment. This library lets you scrape a web page and retrieve particular pieces of data.
To start, let’s open up a Python 3 shell. In this shell, we’ll do all the work for our project:
python3
An interactive shell is opened in which we can write our Python code:
Python 3.8.5 [v3.8.5:580fbb018f, Jul 20 2020, 12:11:27] [Clang 6.0 [clang-600.0.57]] on darwin Type "help", "copyright", "credits" or "license" for more information. >>>
Next, let’s import the bs4 library into our code. We must import any external libraries that we want to use before we can reference them in a program or the shell. Here’s the command we’ll use to import the bs4package:
>>> from bs4 import BeautifulSoup Traceback [most recent call last]: File "", line 1, in ModuleNotFoundError: No module named 'bs4'
Our code returns a ModuleNotFoundError when we try to import our
package. This means that we can’t continue writing our program. Python cannot locate the package modules that we need to write our program. Let’s fix this error by installing the bs4 library:
>>> pip install bs4
This command results in another error:
File "", line 1
pip3 install bs4
^
SyntaxError: invalid syntax
It appears as if we cannot install bs4 using the pip3 command in the Python shell. pip3 is the package installer for Python 3 packages.
The Solution
We’ve tried to install the bs4 package from the
Python interpreter.
You can tell because we’ve opened Python 3 using the python3 command and then we’ve executed the pip3 install command.
Python returns a pip install invalid syntax error because pip is not a keyword in Python. pip is a command line tool that must be run from a command line shell.
To fix this error, we must first exit our Python shell:
>>> exit[]
The exit[]
command tells Python to close the interpreter that is open. Next, we can install bs4 from the command prompt:
pip3 install bs4
This command will install the pip library onto our system. Once this command has executed, we can open up a new Python shell:
python3
Our new shell should have access to the bs4 library. We can test this by importing bs4 into our code:
>>> from bs4 import BeautifulSoup >>>
No error is raised. This means that the import was successful. We can now use bs4 in our program.
Conclusion
The pip install invalid syntax error is raised when you try to install a Python package from the interpreter. To fix this error, exit your interpreter and run the pip install command from a command line shell.
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