cheatsheet.py

# Hello. This is a commant, and as such
# getting ignored by the interpreter


# Types I -- Primitives
1       # This is an integer (int)
1.1     # This is a float (float)
"blah"  # This is a string (str )
True    # This is a boolean (bool)
None    # This is not anything (NoneType)


""" This is a multi line string.

    These are also commonly used
    for comments, and for code
    documentation in particular
"""


# Assignment Operator
spam = 42
eggs = 'the meaning of life'

""" We can now access spam and eggs, and
    get or set their respective values
"""

ham = spam


# I / O
something = input('> ')
print('you entered', something)


# Comparison Operators
print(
    spam == 42,    # True
    spam > 0,      # True
    spam == eggs,  # False
    spam != eggs   # True
)


# Arithmetic Operators
print(
    1 + 1,       # 2
    spam - 1,    # 41
    spam * spam  # 1764
    (1 + 1) / 3  # 0.6666666666666666
)

""" Other arithmetic operators are % (modulo),
    ** (power); for more esoteric functions
    concerned with rounding and such please
    have a look at the math library...
    https://docs.python.org/3.5/library/math.html
"""


# Module Imports
# https://www.xkcd.com/353/
import math
print(math.sqrt(9))  # 3

from math import pi
print(pi)            # 3

from math import pi as weirdnumber
print(weirdnumber)   # 3


# Logical Operators
print(
    not False,          # True
    True is False,      # False
    True is not False,  # True
    True and False,     # False
    False or True,      # True
)


# Types II -- Casting
print(
    type(spam) == int,  # True
    float(spam),        # 42.0
    spam == '42',       # False
    str(spam) == '42',  # True
    spam == int('42')   # True
)


# Lists
values = [1, 2, 3]
print(
    2 in values,      # True
    4 not in values,  # True
    len(values)       # 3
)

values.append(4)
print(values)         # [1, 2, 3, 4]

values.reverse()
print(values)         # [4, 3, 2, 1]

last = values.pop()
print(last, values)   # 1 [4, 3, 2]

values[2] = 42
values[0] = values[0] + values[1]
print(
    values,            # [7, 3, 42]
    values.index(42),  # 2
    values[-1],        # 42
    values[1:3],       # [3, 42]
    values[:2]         # [7, 3]
)


# Control Flow I -- Conditionals
if int(something) in values:
    print(something, 'is in', values)

elif something == eggs:
    print(something, 'is not in', values, 'but it is', eggs)

else:
    print(something, 'is neither in', values, 'nor is it', eggs)


# Control Flow II -- Loops
while input('> ') != str(spam):
    print('Please try again!')

while True:
    guess = input('> ')

    if not guess:
        continue

    if int(guess) == spam:
        break

    print('Please try again!')


# Control Flow III -- Iteration
result = 0
for value in values:
    result = result + value
print(result == sum(values))  # True


# Functions

def double(value):
    """ A function can (but does not have to)
        accept parameters that are again passed
        as arguments, and accessible within the
        scope of the function like regular
        variables.

        A function may also return a value
        that is available to the caller just
        like any other expression
    """

    return value + value


twenty = double(10)
print(twenty)        # 20
print(double(spam))  # 84