{"id":91,"date":"2020-10-03T01:27:12","date_gmt":"2020-10-03T01:27:12","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=91"},"modified":"2025-03-26T10:20:17","modified_gmt":"2025-03-26T10:20:17","slug":"python-while","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-basics\/python-while\/","title":{"rendered":"Python while"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the Python while<\/code> statement and how to use it to run a code block as long as a condition is true.<\/p>\n\n\n\n

Introduction to the Python while statement #<\/a><\/h2>\n\n\n\n

Python while<\/code> statement allows you to execute a code block repeatedly as long as a condition is True<\/code>. <\/p>\n\n\n\n

The following shows the syntax of the Python while<\/code> statement:<\/p>\n\n\n

while<\/span> condition:  \n   body<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The while<\/code> statement checks the condition at the beginning of each iteration. It’ll execute the body as long as the condition<\/code> is True.<\/p>\n\n\n\n
In the body of the loop, you need to do something to stop the loop at some time. <\/p>\n\n\n\n
Otherwise, you’ll get an indefinite loop<\/strong> that will run forever until you close the application.<\/p>\n\n\n\n
Because the while<\/code> statement checks the condition<\/code> at the beginning of each iteration, it’s called a pretest loop<\/strong>.<\/p>\n\n\n\n
If the condition<\/code> is False<\/code> from the beginning, the while<\/code> statement will do nothing.<\/p>\n\n\n\n
The following flowchart illustrates the while<\/code> loop statement:<\/p>\n\n\n
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\"\"<\/figure>\n<\/div>\n\n\n
Python while statement examples #<\/a><\/h2>\n\n\n\n
Let’s take some examples of using the Python while<\/code> statement.<\/p>\n\n\n\n
1) Simple Python while statement example #<\/a><\/h3>\n\n\n\n
The following example uses a while<\/code> statement to show 5 numbers from 0 to 4 to the screen:<\/p>\n\n\n
max = 5<\/span>\ncounter = 0<\/span>\n\nwhile<\/span> counter < max:\n    print(counter)\n    counter += 1<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
0<\/span>\n1<\/span>\n2<\/span>\n3<\/span>\n4<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
The condition<\/code> is an expression that evaluates to a boolean<\/a> value, either True<\/code> or False<\/code>. <\/p>\n\n\n\n