Cheat Sheet

Sequence of Instructions

Program

A program is a sequence of instructions given to a computer.

Defining a Variable

A variable gets created when you assign a value to it for the first time.

Code

age = 10

Printing Value in a Variable

Code

age = 10

print(age)

Output

10

Code

age = 10

print("age")

Output

age

Variable name enclosed in quotes will print variable rather than the value in it.

If you intend to print value, do not enclose the variable in quotes.

Order of Instructions

Python executes the code line-by-line.

Code

print(age)

age = 10

Output

NameError: name 'age' is not defined

Variable 'age' is not created by the time we tried to print.

Spacing in Python

Having spaces at the beginning of line causes errors.

Code

a = 10 * 5

b = 5 * 0.5

b = a + b

Output

File "main.py", line 3

b = a + b

^

IndentationError: unexpected indent

Variable Assignment

Values in the variables can be changed.

Code

a = 1

print(a)

a = 2

print(a)

Output

1

2

Examples of Variable Assignment

Code

a = 2

print(a)

a = a + 1

print(a)

Output

2

3

Code

a = 1

b = 2

a = b + 1

print(a)

print(b)

Output

3

2

Expression

An expression is a valid combination of values, variables and operators.

Examples

a * b

a + 2

5 * 2 + 3 * 4

BODMAS

The standard order of evaluating an expression

• Brackets (B)
• Orders (O)
• Division (D)
• Multiplication (M)
• Addition (A)
• Subtraction (S)

Step by Step Explanation

(5 * 2) + (3 * 4)

(10) + (12)

22

Code

print(10 / 2 + 3)

print(10 / (2 + 3))

Output:

8.0

2.0