Python Cheatsheet

Python syntax and common patterns – Not an exhaustive list, just a few things I find handy to keep in a cheat sheet.

Variables and Types

  • Lists: ["a" , "b", "c"]
  • Tuples: Immutable lists ("a", "b", "c")
  • Dicts: key/value dictionaries/hashtable {"a": 1, "b":2}
  • Sets: key-only dict {"a", "b"}
    • requires property uniqueness
    • Faster lookup for existence
    • unordered, mutable

List Methods


Dict Methods

d.get("i", "default") 
d.update({"j": 5}) # add to dict
d.keys() # iterable of keys
d.values() # iterable of values
d.items() # iterable of both


  • List Comprehension: create new lists in loops
    original = ["A", "B", "C" ]
    converted = [
      i.lower() for i in original


  • Lambda functions: one line functions
    cubed = lambda i: i**3
  • Variable length arguments
    do_something(*args, **kwargs)
      for arg in args:
          #iterable of non-keys arguments
      for key, value in kwargs.items():
          # dict of keyed arguments, note items() to allow for iteration

Exception Handling

try: a.keys()
except Exception as e:
    print("err", e)
Written on December 15, 2018