An Introduction to Interactive Programming in Python - Week zero

Comments — CodeSkulptor

Non-computational parts of the program that textually describe the behavior of the program.
Comments begin with

#

, everything to right
of the hash is ignored by Python.
Comments should be frequent so you and others can understand the code.
Lecture examples - CodeSkulptor
More examples - Comments,
Strings, and Print

Strings — CodeSkulptor

Sequence of characters enclosed by a pair of single or double quotes
Examples are

"cats hate dogs"

and

'Strings
are fun!'

.
Strings are one kind of data in Python. Their data type is denoted

str

.
Lecture examples - Hello World
More examples - Comments, Strings, and Print

Numbers — Arithmetic Expressions

There are two kinds of numerical data in Python:
integers and
decimal numbers.
Integers correspond to the data type

int

.
Decimal numbers are represented by floating-point numbers corresponding to the data type

float

.
Floating-point numbers have around 15 decimal digits of accuracy.
In CodeSkulptor, all numbers (even integers) are represented internally as floating-point numbers.
Lecture examples - Arithmetic
Expressions
More examples - Floats
and Ints

Arithmetic Operators — Arithmetic Expressions

Five basic arithmetic operators; addition (

+

),
subtraction (

-

), multiplication (

*

),
division (

/

) and exponentiation (

**

)
CodeSkulptor implements a subset of Python 2. In Python 2, the division operator (

/

)
returns a float approximation to the exact answer if either of the operands is a float. If both operands are integers, division returns the exact answer round down to the nearest integer.
The integer division operator

//

returns
the quotient of two numbers..
Lecture examples - Arithmetic
Expressions
More examples - Arithmetic
Operations, Division

Arithmetic Expressions — Arithmetic Expressions

An arithmetic expression is either a number or an operator applied to two arithmetic expressions.
Arithmetic expressions are entered as a sequence of numbers and arithmetic operators.
Expressions are formed by grouping operators and operands via precedence: "Please excuse my dear Aunt Sallie"; parentheses, exponentiation, multiplication, division, addition, subtraction.
Lecture examples - Arithmetic Expressions
More examples - Order
of Operations for Arithmetic Expressions, Possible
Errors for Arithmetic Expressions

Variables — Variables

Variable names consist of a sequence of letters, number and underscores (

_

).
Variable names start with a letter or underscore and are case sensitive.
Single equals (

=

) is used for assignment
to variables. Double equals (

==

) is used for testing
equality.
Lecture examples - Variables
More examples - Variable Naming, Vabiable
Assignment, Variable
Operations, Formulas

From: https://class.coursera.org/interactivepython-005/wiki/view?page=week0