Why does "pip install" inside Python raise a SyntaxError?

Understanding the difference: Command Line vs Python Interpreter

Python interpreter and Command line - while looking somewhat similar in form, perform entirely different functions and roles.

• Python Interpreter: This is your sandbox. This is where you write, rewrite, and check your fun and not-so-fun Python code snippets.
• Command Line: Act as a system power-user. This is the place to run system-level commands like pip install package_name.

If playing with multiple Python versions, here's how to specify which Python runtime pip should use:

Python v3.x:

python3 -m pip install package_name
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Python v2.x:

python2 -m pip install package_name
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Should you need to perform pip install within a Python script, subprocess module happens to be just the tool for that:

# Who needs a CLI when you got Python, right? *evil smirk*
import subprocess
subprocess.check_call(['pip', 'install', 'package_name'])
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Dealing with the peculiarities of pip

If it's over 10, it's tricky. pip._internal is your only friend if you want to leverage pip's power programmatically post version 10.x.

# Quirky but it WORKS! 🙃
import pip._internal as pip
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Reminders:

1. This method, while it works, is generally not recommended due to pip’s internal APIs potentially changing with each release.
2. If the error is related to __main__.py within pip's installation directory, make sure the PATH configuration for your environment is correct and both Python and pip are installed properly.

For regular pip updates and problem solving, issue #7498 has your back!

Syntax is your friend (or foe if not followed)

Whether you're a Pythonista or a pip wizard, correct syntax holds the keys to the kingdom. Here's the right way and the wrong way to do it:

Right on the command line:

pip install package_name
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Wrong in Python Interpreter:

# Seriously, stop doing this... It won't work! 
pip install package_name
SyntaxError: invalid syntax
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For pip parameters, remember that Python's interpreter doesn't appreciate parameters like --help:

# Never in the Interpreter. Being a rebel isn't helpful in the coding world.
pip --help
SyntaxError: invalid syntax
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