While loop

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While loops
Sometimes we are not sure how long sometimes will take. For example, how long a car driver would be adding petrol. A program could be (pseudocode):

while petrol_filling:
   increase price
   show price
   add petrol

Python has the while keyword.  Lets build an extended ‘guess the number game’:

x = 0
while x != 5:
   x = int(input("Guess a number:"))
   
   if x != 5:
      print("Incorrect choice")

print("Correct")

This will keep asking a number until the number is guessed.   This is defined in the line: while x != 5, or in English,  “while x is not equal to five, execute”.

Illustrated:
while-loop
The program keeps repeating the code block while the condition (x!=5) is True. Once x equals 5, the program continues.

Infinite loops
If a condition in a while loop is never met, it could cause the program to run forever or to freeze/crash.


For loops
Functions

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