Expressions

A command that returns a value:

>>> 2 + 2
4
>>> abs(-2)
2

Python follows standard order of operations

>>> 3 + 5 * 2
13

Types

All values have types

>>> type(1)
int

>>> type(26.2)
float

>>> type('hello world')
str

Types are important because they tell the program how to act

>>> 'Brad' + 'Pitt'
BradPitt

>>> 75 + 2
77

But they can also be confusing

>>> 15.0 / 2
7.5

>>> 15 / 2
7

• Old school (Python 2): Any combination of two integers is an integer
• New school (Python 3): >>> from __future__ import division

Variables

A variable is a name that has a value associated with it

>>> x = 27
>>> x
27

It works just like the value itself

>>> 10 + x * 2
64

It won’t change unless you assign a new value to it directly

Errors

Errors tell you that your program isn’t working, and they also tell you where it isn’t working and what went wrong. It’s very important to read error messages carefully.

>>> print("The high temperature today is going to be: " + 71)