python.md

• class definition

class Blah:
     def __init__(self, x):
         self.val = x
         self.something = None
         self.something_else = None

• enumerate

for i, x in collection:
  element = collection[i]
  x == element # returns true

• deep copy

import copy

copy.deepcopy(thing)

• random

  • import: import random
  • random.randint(a, b) for a random integer in [a, b]
  • random.choice(seq) to pick a random element in the sequence
  • random.random() to get a random floating point number in [0.0, 1.0)
  • docs

• sets: create using set(), use frozensets if you want immutable sets (useful if you want sets of sets because sets cannot contain mutable objects)

• random string stuff: lower(), isalnum(), len() etc

• sorting tuples: merged = sorted(some_collection_of_tuples, key = lambda x: x[0])

• dictionaries: dict.get(key, default_value) -> returns default_value if key not in dict

• this * thing:

  • say m = [[1, 2], [3, 4], [5, 6]]. Then zip(*m) is equivalent to zip([1, 2], [3, 4], [5, 6]) so * allows us to specify multiple arguments (lists) as one (list of lists).

  >>> zip([1, 2], [3, 4], [5, 6])
  [(1, 3, 5), (2, 4, 6)]

• reversing a list: either do list(reversed(the_list)) or the_list[::-1]

  • traversing a reversed range: for i in reversed(range(10)) # 9, 8, ..., 0

• list functions: pop() deletes the last element of the list, or if specified, the element at an index

infinity

positive_inf = float("inf")
negative_inf = float("-inf")

# can be compared to other numbers (ints, floats, doubles)

collections (ordered dict, deques) | docs

sockets | docs