The indented code is called a block. A block is made up of lines of code that are indented at the same level. The indentation is how Python tells what parts is inside the if statements block and what isn't. A block begins when the indentation increases and ends when the indentation returns to its previous level.

Truthy and Falsey Values and bool() function¶

In the following example, blank string is Falsey, all others are Truthy. You can always see for yourself which values are Truthy or Falsey by passing them into the bool() function e.g. bool('') returns False

print('Enter a name:')
name = input()
if (name):
  print('Thank you for entering a name')
else:
  print('You did not enter a name')

Enter a name:

You did not enter a name

While Loops¶

Syntax

while True:
  # do something

In the IDLE interactive shell, if you get stuck with an infinite loop, press Ctrl+C for keyboard interrupt.

Break statement¶

The break statement causes the execution to immediately leave the loop without re-checking the condition.

name = ''
while True:
  print('Enter your name')
  name = input()
  if name == 'your name':
    break
print('Thank you')

Enter your name
your name
Thank you

Continue statement¶

The continue statement causes the execution to immediately jump back to the start of the loop and re-check the condition.

spam = 0
while spam < 5:
  spam = spam + 1
  if spam == 3:
    continue
  print('spam is ' + str(spam))

spam is 1
spam is 2
spam is 4
spam is 5

For Loops & Range() Function¶

for loops will loop specific number of times. Keywords break and continue can be used in for loops.

seq = [1,2,3,4,5]
for item in seq:
    print('hello')

hello
hello
hello
hello
hello

The range() function is a generator for generating a sequence or list of integers. The function range() is called with one, two or three arguments.

range(5)

range(0, 5)

list(range(1, 5))

[1, 2, 3, 4]

Range() with 1 argument

for i in range(5):
    print(i)

# range(5) returns range(0, 5)

Range() with 2 arguments

for i in range(12, 16):
    print(i)

Range() with 3 arguments

for i in range(0, 10, 2):
    print(i)

for i in range(5, -1, -1):
    print(i)

5
4
3
2
1
0

Useful Resources¶

Visualize Python, Java, Javascript, Typescript and Ruby Code Execution [Link]

Operator	Meaning
==	Equal to
!=	Not equal to
<	Less than
>	Greater than
<=	Less than or equal to
>=	Greater than or equal to

Table of Contents

Flow Control ¶

Boolean Values¶

Comparison Operators¶

Boolean/ Logical Operator¶

If, Else and Elif Statements¶

Block & Indentation¶