[Tut] Python range() Function — A Helpful Illustrated Guide

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Python range() Function — A Helpful Illustrated Guide

The Python

Code:

range()

function creates an iterable of subsequent integers within a given range of values. You can pass either only a

Code:

stop

argument in which case the

Code:

range

object will include all integers from to

Code:

stop

(excluded). Or you can pass

Code:

start

,

Code:

stop

, and

Code:

step

arguments in which case the range object will go from

Code:

start

to

Code:

step

using the given

Code:

step

size. For example,

Code:

range(3)

results in

Code:

0, 1, 2

and

Code:

range(2, 7, 2)

results in

Code:

2, 4, 6

.



Here are some examples of how to use the

Code:

range()

built-in function:

Code:

>>> range(10) range(0, 10) >>> print(range(10)) range(0, 10) >>> print(*range(10)) 0 1 2 3 4 5 6 7 8 9 >>> range(1, 10, 3) range(1, 10, 3) >>> print(*range(1, 10, 3)) 1 4 7

Note that in any case, a range object is returned. The range object is an iterable of values—but the values are only generated as they’re actually needed. You can use the asterisk operator to unpack all values into the print function with

Code:

print(*range(10))

. Python waits as long as possible to generate the values of the iterable.

Syntax Range Function

You can use the

Code:

range()

function with three different argument lists: (i) with the

Code:

stop

argument only, (ii) with the

Code:

start

and

Code:

stop

arguments, or (iii) with the

Code:

start

,

Code:

stop

, and

Code:

step

arguments.

Code:

Syntax: range(stop) range(start, stop) range(start, stop, step)

Arguments |

Code:

start

|
An integer defining the first element of the

Code:

range

iterable

|

Code:

stop

|
An integer defining the last element. However, this element is not included in the r

Code:

ange

iterable.

|

Code:

step

|
An integer defining the difference between two subsequent elements in the

Code:

range

iterable.

Return Value |

Code:

range

|
Returns an iterable range object that allows you to iterate over all values from

Code:

start

to

Code:

step

using the

Code:

step

size.

Interesting fact: the

Code:

range()

“function” is technically not a normal function but a constructor method of the

Code:

range

class. Thus, it creates a new range object.

How Math Genius Gauss Hacked His Teacher’s Exercise With the Range Function

Do you know the following story of the brilliant mathematician Carl Friedrich Gauss? When 8-year old Gauss went to school, his math teacher sought a few minutes of breathing pause. He told his class to solve the problem of adding all subsequent numbers from 1-100:

Code:

1+2+3+...+100

.

But as little Gauss promptly reported the solution, the short pause was over before it began.

Surprised (and a bit grumpy as the story goes), the teacher asked the boy how he had come up with a solution so quickly. Gauss explained his simple solution. He organized the sequence into pairs of numbers each summing up to 101:

Code:

1+100,2+99,3+98,...,50+51

. There are 50 such pairs, so the total result was

Code:

50*101=5050

.

Yet, the modern-time little Gauss would be even lazier. He would type the following one-linerinto his mobile Python app:

Code:

sum(range(1,101))

.

The

Code:

range()

function returns a sequence starting from the first value (inclusive) and ending in the second value (exclusive). The sum function sums up the values of this sequence. Combining both functions sums up the sequence from 1-100—faster than the brilliant Carl Friedrich Gauss.

Python range() With One Argument Stop

You can use the

Code:

range()

function with one argument

Code:

stop

. In this case, the range object goes from

Code:

start=0

to the

Code:

stop

argument (excluded) by using the default step size of one.



Here’s the example:

Code:

for i in range(5): print(i)

The output is:

Code:

0 1 2 3 4

Python range() With Two Arguments Start + Stop

You can use the

Code:

range()

function with two arguments

Code:

start

and

Code:

stop

. In this case, the range object goes from

Code:

start

to the

Code:

stop

integer value (excluded) by using the default step size of one.



Here’s the example:

Code:

for i in range(1, 5): print(i)

The output is:

Code:

1 2 3 4

Python range() With Three Arguments Start + Stop + Step

You can use the

Code:

range()

function with three arguments

Code:

start

,

Code:

stop

, and

Code:

step

. In this case, the

Code:

range

object goes from

Code:

start

to the

Code:

stop

integer value (excluded) by using the default step size of

Code:

step

.



Here’s the example:

Code:

for i in range(1, 5, 2): print(i)

The output is:

Code:

1 3

Interactive Shell Exercise About The Range Function

The following code snippet matches men with women—the idea is to match the i-th man with the i-th woman, assuming that both lists have the same size. How to change the code to accomplish this task?

https://trinket.io/embed/python/5ab4ae4f21

Exercise: Replace the

Code:

XXXX

placeholder in the code to match the i-th man with the i-th woman!

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Solution: The following code solves the exercise.

Code:

men = ['Bob', 'Carl', 'Frank'] women = ['Ann', 'Alice', 'Liz'] for i in range(len(men)): print(men[i] + ' dances with ' + women[i])

The idea is to use the

Code:

len()

function to determine the

Code:

stop

argument automatically with

Code:

range(len(men))

. Note that

Code:

range(len(women))

,

Code:

range(3)

, and

Code:

range(0, 3)

, and

Code:

range(0, 3, 1)

would all solve the problem equally well.

Python range() With Negative Step Size

You can also use the range() function with negative step size. The meaning is “move from right to the left using the negative step size as the difference between two subsequent values. In this case, the start argument should be larger than the stop argument.



Here’s an example:

Code:

for i in range(4,0,-2): print(i)

The output is:

Code:

4 2

Note that the

Code:

stop

argument is still not included in the

Code:

range

object.

Range Puzzle

Puzzles are a great and effective way to improve your Python skills. Can you solve this range puzzle?

Code:

# Python Puzzle print(sum(range(0,7)))

What is the output of this code snippet?

You can check whether you solved this puzzle correctly, and determine whether you’re a master coder on our Puzzle app Finxter.com:



Are you a master coder?
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Summary

The Python

Code:

range()

function creates an iterable of subsequent integers within a given range of values.

You can pass either only a

Code:

stop

argument in which case the

Code:

range

object will include all integers from to

Code:

stop

(excluded). For example,

Code:

range(3)

results in

Code:

0, 1, 2

:

Code:

for i in range(3): print(i) ''' OUTPUT: 0 1 2 '''

As an alternative, you can pass

Code:

start

,

Code:

stop

, and

Code:

step

arguments in which case the range object will go from

Code:

start

to

Code:

step

using the given

Code:

step

size. For example,

Code:

range(2, 7, 2)

results in

Code:

2, 4, 6

:

Code:

for i in range(2, 7, 2): print(i) ''' OUTPUT: 2 4 6 '''

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