We have discussed if
Statement in our previous Article “Python – Control Flows – The if Statement“. The if
Statement is one of the control statements in Python, used to control the flow of the Program depending on the conditional expression. The code is written inside the if
Statement is going to execute only once depending on the conditional expression. How to repeatedly execute the statements? Where while
Statement comes into the picture.
The while
Statement in Python
This is a Compound Statement and the statements written in while
Statement is going to execute as long as the conditional expression evaluates to true. It is important to note that one of the statements written in while
should be helpful to make the conditional expression false. Otherwise, the loop will execute infinitely.
In the below example, the “a = a – 1” statement is helpful to make the conditional expression false after a couple of iterations. This statement is important; otherwise, the loop will execute infinitely.
>>> a = 3 >>> while a > 0: ... print(a) ... a = a - 1 ... 3 2 1
else
within while
in Python
while
Statement has two blocks. The code written in while
block is going to execute repeatedly as long as the conditional expression is true. When the expression is false, the statements written in else
block will execute. The else
Statement within while
Statement is optional.
Below is the code example, which displays each element in a list. Once all elements are displayed, the statements in else
block will execute.
>>> l = ["Australia", "Belgium", "Canada"] >>> i = 0 >>> while i < 3: ... print(l[i]) ... i = i + 1 ... else: ... print("-- end of list --") ... Australia Belgium Canada -- end of list -- >>>
This is IMPORTANT to note that the statements written in else
block will execute ONLY once when the conditional expression evaluates to false.
We discuss more topics as we go.
/Shijit/
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