- 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
- 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
- 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 typefloat. - 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
- 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
- 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
- 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