A function is a named sequence of statements that performs a computation

Calling Functions

• We’ve already done this
• Use the function name followed by parens containing arguments to pass

Example

• int is a function
• It takes one argument and returns a value

num = int("42")

Return value

• The name for the value returned from a function

Built-in function

• Python includes many functions that we may have use for

Input

• Displays an optional prompt and returns user input

min and max

• min and max return the minimum and maximum of their arguments

>>> min(1, 3)
1
>>> max(12, 4)
12

Iterables

• min and max can also operate on iterables such as strings

>>> min("abc")
'a'
>>> max("green")
'r'

len

• len can be used to return the length of a value

>>> len("Hello")
5
>>> len("Blue")
4
>>> len("")
0

Type conversions

• int, float, and str can be used to convert types

>>> int("1")
1
>>> float("1.5")
1.5
>>> str(1.5)
'1.5'

math

• The math module can be used to access various math functions
• import math can be used to create the math object used to access the module
• A module is a file containing Python definitions and statements

Dot notation

• Modules contain functions and variables
• These can be accessed using the . character

import math

print(math.pi)

Example

import math

dist = input("Distance to building: ")
height = input("Building height: ")

angle_rad = math.atan(float(height) / float(dist))
angle_deg = angle_rad * 180 / math.pi

print("Angle to top:", angle_deg)

help

• help can be used to provide information about an object
• help(math) provides information about available math functions

random

• The random module provides access to pseudorandom numbers
• These numbers will appear random, but are generated deterministically
• They should not be used in cryptography

Example

import random

# Print random number between 0.0 and 1.0
print(random.random())

randint

• randint returns a random integer between bounds

# Returns a number between 1 and 10 inclusive
random.randint(1, 10)

choice

• choice selects one item from an iterable

# Pick a, b, or c
random.choice("abc")