Python Cheatsheet

• Python (python.org)
• Learn X in Y minutes
• Regex in python

>>> print("Hello, World!")
Hello, World!

The famous "Hello World" program in Python.

age = 18         # age is of type int
name = "John"     # name is now of type str
print(name)

Python can't declare a variable without assignment.

>>> msg = "Hello, World!"
>>> print(msg[7:9])
llo

mylist = []
mylist.append(1)
mylist.append(2)
for item in mylist:
    print(item) # prints out 1,2

num = 200
if num > 0:
    print("num is greater than 0")
else:
    print("num is not greater than 0")

for item in range(5):
    if item == 3: break
    print(item)
else:
    print("Finally finished!")

s = "Hello"
print(s.upper())  # 'HELLO'
print(s.lower())  # 'hello'
print(s.replace("l", "x"))  # 'Hexxo'
print(s[1:4])  # 'ell'

a = 5
b = 2.5
print(a + b)  # 7.5
print(a // 2)  # 2 (floor division)
print(a ** 3)  # 125 (power)

t = (1, 2, 3)
print(t[1])  # 2
print(t.count(2))  # 1

s = {1, 2, 3}
s.add(4)
print(s)  # {1, 2, 3, 4}

d = {"a": 1, "b": 2}
print(d["a"])  # 1
d["c"] = 3

lst = [0, 1, 2, 3, 4]
print(lst[1:4])    # [1, 2, 3]
print(lst[-2:])    # [3, 4]
print(lst[::-1])   # [4, 3, 2, 1, 0]

squares = [x*x for x in range(5)]  # [0, 1, 4, 9, 16]
evens = [x for x in range(10) if x % 2 == 0]

x = 10
if x > 0:
    print("Positive")
elif x == 0:
    print("Zero")
else:
    print("Negative")

for i in range(3):
    print(i)
for idx, val in enumerate(['a', 'b']):
    print(idx, val)
while x > 0:
    x -= 1