For , If and While are the primitive compound statements/loops in Python. In this tutorial, we will be covering only the Python while statement.
Python While Loop:
Python while loop is used to execute a set of statements as long as the condition is true. The below code prints the numbers from 1 to 10.
a=1 while(a<=10): print(a) a+=1 print("Numbers 1 to 10 are printed")
The above code works as below:
- Initializing variable a to 1
- While statement checks if the variable ‘a’ is less than or equal to 10
- If the condition is True, ‘a’ will be incremented by 1.
- When the last line has encountered, the condition of the while statement will be tested again.
- So the above code prints all the numbers from 1 to 10.
- When ‘a’ becomes 11, the condition becomes false and the loop will be exited.
- Whatever the statement was written outside the while loop will be executed.
We have to be careful about the infinite loop while using the Python ‘while’ statement. In case, we forgot to increment the variable ‘a’, it will result in an infinite loop.
a=1 while(a<=10): print(a) print("Numbers 1 to 10 are printed")
Python While and ELSE:
With the else statement we can run a block of code once when the condition given in the while statement becomes false.
a=11 while(a<=10): print(a) a+=1 else: print("a is greater than 10")
Looping through Lists:
We can loop through lists, strings, and tuples using the while loop.
l=[8,9,1,4,5] length=len(l) i=0 # since the index starts with zero while(i<length): print(l[i]) i+=1
IF inside while loop:
We can also use the IF loop inside the while loop. The below code is to print the even numbers from 1 to 10.
a=1 while(a<=10): if a%2==0: print(a) a+=1
You can modify the above code to print the odd numbers. Try more examples on while loops.