{"id":89,"date":"2020-10-03T01:24:43","date_gmt":"2020-10-03T01:24:43","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=89"},"modified":"2025-03-26T10:20:00","modified_gmt":"2025-03-26T10:20:00","slug":"python-for-range","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-basics\/python-for-range\/","title":{"rendered":"Python for Loop with Range"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the Python for<\/code> loop and how to use it to execute a code block a fixed number of times.<\/p>\n\n\n\n

Introduction to Python for loop statement with the range() function #<\/a><\/h2>\n\n\n\n

In programming, you often want to execute a block of code multiple times. To do so, you use a for<\/code> loop.<\/p>\n\n\n\n

The following illustrates the syntax of a for<\/code> loop:<\/p>\n\n\n

for<\/span> index in<\/span> range(n):\n    statement<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, the index<\/code> is called a loop counter<\/strong>. And n<\/code> is the number of times that the loop will execute the statement<\/code>.<\/p>\n\n\n\n
The name of the loop counter doesn’t have to be index<\/code>, you can use whatever name you want.<\/p>\n\n\n\n
The range()<\/code> is a built-in function in Python. It’s like the print()<\/code> function in the sense that it’s always available in the program.<\/p>\n\n\n\n
The range(n)<\/code> generates a sequence of n<\/code> integers starting at zero. It increases the value by one until it reaches n<\/code>.<\/p>\n\n\n\n
So the range(n)<\/code> generates a sequence of numbers: 0<\/code>,1<\/code>, 2<\/code>, …n-1<\/code>. Note that it’s always short of the final number (n<\/code>).<\/p>\n\n\n\n
The following diagram illustrates the for<\/code> loop statement:<\/p>\n\n\n
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\"Python<\/figure>\n<\/div>\n\n\n
The following example shows how to use the for<\/code> loop with the range()<\/code> function to display 5 numbers from 0 to 4 to the screen:<\/p>\n\n\n
for<\/span> index in<\/span> range(5<\/span>):\n    print(index)<\/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
In this example, the for<\/code> loop executes the statement print(index)<\/code> exactly five times.<\/p>\n\n\n\n
If you want to show 5 numbers from 1 to 5 on the screen, you can do something like this:<\/p>\n\n\n
for<\/span> index in<\/span> range(5<\/span>):\n    print(index + 1<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
1<\/span>\n2<\/span>\n3<\/span>\n4<\/span>\n5<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, we increase the index<\/code> by one in each iteration and print it out. However, there’s a better way to do it.<\/p>\n\n\n\n
Specifying the starting value for the sequence #<\/a><\/h3>\n\n\n\n
By default, the range()<\/code> function uses zero as the starting number for the sequence. <\/p>\n\n\n\n
In addition, the range()<\/code> function allows you to specify the starting number like this:<\/p>\n\n\n
range(start, stop)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, the range()<\/code> function increases the start<\/code> value by one until it reaches the stop<\/code> value.<\/p>\n\n\n\n
The following example uses a for<\/code> loop to show five numbers, from 1 to 5 to the screen:<\/p>\n\n\n
for<\/span> index in<\/span> range(1<\/span>, 6<\/span>):\n    print(index)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
1<\/span>\n2<\/span>\n3<\/span>\n4<\/span>\n5<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Specifying the increment for the sequence #<\/a><\/h3>\n\n\n\n
By default, the range(start, stop)<\/code> increases the start<\/code> value by one in each loop iteration.<\/p>\n\n\n\n
To increase the start<\/code> value by a different number, you use the following form of the range()<\/code> function:<\/p>\n\n\n
range(start, stop, step)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this form, you can specify the value that the range()<\/code> function should increase.<\/p>\n\n\n\n
The following example shows all the odd numbers from 0 to 10:<\/p>\n\n\n
for<\/span> index in<\/span> range(0<\/span>, 11<\/span>, 2<\/span>):\n    print(index)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
0<\/span>\n2<\/span>\n4<\/span>\n6<\/span>\n8<\/span>\n10<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Using Python for loop to calculate the sum of a sequence #<\/a><\/h2>\n\n\n\n
The following example uses the for loop statement to calculate the sum of numbers from 1 to 100:<\/p>\n\n\n
sum = 0<\/span>\nfor<\/span> num in<\/span> range(101<\/span>):\n    sum += num\n\nprint(sum)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
5050<\/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
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n