{"id":41,"date":"2024-01-24T14:02:32","date_gmt":"2024-01-24T14:02:32","guid":{"rendered":"https:\/\/learnpython.elegantwallp.com\/?p=41"},"modified":"2024-01-24T14:02:35","modified_gmt":"2024-01-24T14:02:35","slug":"python-while","status":"publish","type":"post","link":"https:\/\/learnpython.elegantwallp.com\/2024\/01\/24\/python-while\/","title":{"rendered":"Python while"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you\u2019ll 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<\/code> statement<\/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\u00a0while<\/code>\u00a0statement:<\/p>\n\n\n\n

while condition: body<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The\u00a0condition<\/code>\u00a0is an expression that evaluates to a\u00a0boolean\u00a0value, either\u00a0True<\/code>\u00a0or\u00a0False<\/code>.<\/p>\n\n\n\n
The while<\/code> statement checks the condition at the beginning of each iteration. It\u2019ll 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\u2019ll 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\u2019s 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\n
\"\"<\/figure>\n\n\n\n
Python while statement examples<\/h2>\n\n\n\n
Let\u2019s take some examples of using the Python while<\/code> statement.<\/p>\n\n\n\n
1) Simple Python while statement example<\/h3>\n\n\n\n
The following example uses a\u00a0while<\/code>\u00a0statement to show 5 numbers from 0 to 4 to the screen:<\/p>\n\n\n\n
max = 5 counter = 0 while counter < max: print(counter) counter += 1<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
0 1 2 3 4<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
How it works.<\/p>\n\n\n\n
    \n
  • First, define two variables called max<\/code> and counter<\/code> with the initial values of five and zero.<\/li>\n\n\n\n
  • Second, use the while<\/code> statement with the condition counter < max<\/code>. It\u2019ll execute the loop body as long as the value of the counter<\/code> is less than the value of max<\/code>.<\/li>\n\n\n\n
  • Third, show the value of the counter<\/code> variable and increase it by one in each iteration. After five iterations, the value of the counter<\/code> is 5, which makes the condition counter < max<\/code> evaluates to False<\/code> and hence the loop stops.<\/li>\n<\/ul>\n\n\n\n
    2) Using the Python while statement to build a simple command prompt program<\/h3>\n\n\n\n
    The following example uses the\u00a0while<\/code>\u00a0statement to prompt users for input and echo the command that you entered back. It\u2019ll run as long as you don\u2019t enter the\u00a0quit<\/code>\u00a0command:<\/p>\n\n\n\n
    command = '' while command.lower() != 'quit': command = input('>') print(f\"Echo: {command}\") <\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Note that the command.lower()<\/code> returns the command in lowercase format. This allows you to enter the quit command such as quit<\/code>, QUIT<\/code>, or Quit<\/code>.<\/p>\n\n\n\n
    Example output:<\/p>\n\n\n\n
    >Hi Echo: Hi >Python while Echo: Python while >quit Echo: quit<\/code><\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
    Summary: in this tutorial, you\u2019ll learn about the Python while statement and how to use it to run a code block as long as a condition is true. Introduction to the Python while statement Python while statement allows you to execute a code block repeatedly as long as a condition is True. The following shows the syntax of the Python\u00a0while\u00a0statement: The\u00a0condition\u00a0is an […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-41","post","type-post","status-publish","format-standard","hentry","category-3-control-flow"],"_links":{"self":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/41","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/comments?post=41"}],"version-history":[{"count":1,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/41\/revisions"}],"predecessor-version":[{"id":42,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/41\/revisions\/42"}],"wp:attachment":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/media?parent=41"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/categories?post=41"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/tags?post=41"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}