Python

Python is an easy-to-learn high-level general-purpose programming language. It is especially suitable for beginners to programming, amateurs/hobbyists, scientists, engineers.

Pros:

• Easy to learn
• High-level
• Dynamically typed
• Simple and readable syntax
• Vast ecosystem
• Large community and help sources
• Rapid prototyping
• Excellent glue language
• Many packages interface with C or other fast languages to achieve performant code
• Interoperable with many other languages

Cons:

• Very slow: About 50 times slower than C. This is not a deal-breaker though for a glue/scripting language, and for prototyping purposes.
• Low-quality packages: There are almost no imposed requirements on packages and compability between packages: Expect compatibility issues, breaking functionality across package versions, unintuitive APIs, and lacking documentation.
• Non-standardized tooling: despite the emphasis on the Pythonic way, there are hilariously many cases of competing tools, packages, and standards: see dependency management, repository structure, unit testing, to name a few.
• Dynamically typed: great for rapid prototyping, not for large frameworks.
• No built-in language support for vector and matrix operations: results in needlessly verbose code for any engineering or data science applications.
• No fluent interface: No support for chaining function calls, which is a common use case in analysis scripts and data manipulation. This results in many data science libraries resorting to the builder pattern, which forces the use of implementing subclasses just to call another function.

Short Python cheatsheets:

• https://www.pythoncheatsheet.org/
• https://quickref.me/python

Run

Script

Action	Code	Details
Start Python script, wait for completion	os.system('python script.py')
Start Python script with arguments, wait for completion	os.system('python script.py -file "hello.csv")

Environment

Environment variables

All snippets require import os. Updates to the environment are not reflected in the os.environ mapping.

Action	Code	Details
Get list of all environment variables	list(os.environ)
Get all environment variables as dict	dict(os.environ)
Check if environment variable exists	'path' in os.environ	Case-insensitive
Get value of environment variable, error if not found	os.environ['path']
Try get value of environment variable, or return None	os.getenv('path')
Try get value of environment variable, or return None	os.environ.get('path')
Try get value of environment variable, or return default value v	os.environ.get('missingvar', v)
Set / update environment variable	os.environ['derp'] = 'hello'
Set environment variable only if it is not yet defined	os.environ.setdefault('derp', 'world')
Delete environment variable, error if not defined	del os.environ['derp']
Delete environment variable, error if not defined	os.environ.pop('derp')
Try delete environment variable	os.environ.pop('derp', None)