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Python for Basic Data Analysis: 1.13 Conditional statements (if-elif-else)

Get started on your learning journey towards data science using Python. Equip yourself with practical skills in Python programming for the purpose of basic data manipulation and analysis.

Conditional statements

Conditional statements check for conditions and determine what code to run depending on the results of the conditions.

Conditional statements controls the flow of a Python program.

if-elif-else

If statements

We can use if statements when we want the code to do something when a condition is met.

Sequence of an if statement:

Step 1 Evaluate condition
Step 2 • If  True  , execute action
• If  False , skip action

Syntax

x = 3
if x >= 2:
    print("x is bigger than or equal to 2")


Example

If-else statements

We can use if-else statements when we want the code to do something else if the condition fails. 

Sequence of an if-else statement:

Step 1 Evaluate condition
Step 2 • If  True  , execute action
• If  False , execute another action

Syntax

x = 30 

if x >= 50:
  print("x bigger than or equals to 50")
else:
  print("x is a number smaller than 50")


Examples

If-elif-else statements

We can use the if-elif-else statement to tell Python to try a different condition if the previous conditions were not met. 

Sequence of an if-elif-else statement:

Step 1 • If the first condition is  True , then execute the first action
• If it is  False , then test for the second condition
Step 2 • If the second condition is  True , then execute the second action
• If it is  False , execute the final else action

Syntax

x = 10
if x > 20:
  print("x is bigger than 10.")
elif x = 20:
  print("x is equals to 20.")
else:
  print("x is neither bigger than 10 or equal to 20.")


Example

Exercises

1. If - Assign 10 to x. If x is bigger than 0, print "x is a positive number".

2. If-else - Assign -50 to y. If x is bigger than 0, print "x is a positive number". Else, print "x is a negative number".

3. If-elif-else - Assign 0 to z. If x is bigger than 0, print "x is a positive number". Else if x is zero, print "x is 0". Else, print "x is a negative number".