Python programs use if commands and conditions to make decisions.

Indentation (4 spaces) is used to show what actions have to be taken.

if

Do something or nothing:

#
if temperature < 17:
    print('It is too cold')
#

if-else

Do one thing or another:

#
if speed > 60:
    print('That is over the national speed limit')
else:
    print('That is inside the national speed limit')    
# 

if-elif-else:

Do one of several things:

#
if mark >= 70:
    grade = 'A' 
elif mark >=60:  
    grade = 'B'
elif mark >=50:
    grade = 'C'
elif mark >=40:
    grade = "D"
else:
    grade = "F"
#