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Python•Foundations

Python range

Overview

The built-in range() function returns an immutable sequence of numbers, commonly used for looping a specific number of times. This set of numbers has its own data type called range.

Note:

Immutable means that it cannot be modified after it is created.

Creating ranges

The range() function can be called with 1, 2, or 3 arguments, using this syntax: range( start, stop, step )

Call range() With One Argument

If the range function is called with only one argument, the argument represents the stop value. The start argument is optional, and if not provided, it defaults to 0. range(10) returns a sequence of each number from 0 to 9. (The start argument, 0 is inclusive, and the stop argument, 10 is exclusive).

Example

Create a range of numbers from 0 to 9:

Formula

x = range(10)

Call range() With Two Arguments

If the range function is called with two arguments, the first argument represents the start value, and the second argument represents the stop value. range(3, 10) returns a sequence of each number from 3 to 9:

Example

Create a range of numbers from 3 to 9:

Formula

x = range(3, 10)

Call range() With Three Arguments

If the range function is called with three arguments, the third argument represents the step value. The step value means the difference between each number in the sequence. It is optional, and if not provided, it defaults to 1. range(3, 10, 2) returns a sequence of each number from 3 to 9, with a step of 2:

Example

Create a range of numbers from 3 to 9:

Formula

x = range(3, 10, 2)

Using ranges

Ranges are often used in for loops to iterate over a sequence of numbers.

Example

Iterate over each value in a range: for i in range(10):

print(i)

Using List to Display Ranges

The range object is a data type that represents an immutable sequence of numbers, and it is not directly displayable. Therefore, ranges are often converted to lists for display.

Example

Convert different ranges to lists:

print(list(range(5)))
print(list(range(1, 6)))
print(list(range(5, 20, 3)))

Slicing Ranges

Like other sequences, ranges can be sliced to extract a subsequence.

Example

Extract a subsequence from a range:

Formula

r = range(10)

print(r[2])
print(r[:3])

Note:

The first print statement returns the value at index 2, and the second print statement returns a new range object, from index 0 to 3.

Membership Testing

Ranges support membership testing with the in operator.

Example

Test if the numbers 6 and 7 are present in a range:

Formula

r = range(0, 10, 2)

print(6 in r)
print(7 in r)

The return value is

True when the number is present in the range, and False when it is not.

Length

Ranges support the len() function to get the number of elements in the range.

Example

Get the length of a range:

Formula

r = range(0, 10, 2)

print(len(r))

Python Generators

Python Arrays

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Learn/Python/Foundations

Python•Foundations

Python range

Overview

The built-in range() function returns an immutable sequence of numbers, commonly used for looping a specific number of times. This set of numbers has its own data type called range.

Note:

Immutable means that it cannot be modified after it is created.

Creating ranges

The range() function can be called with 1, 2, or 3 arguments, using this syntax: range( start, stop, step )

Call range() With One Argument

Example

Create a range of numbers from 0 to 9:

Formula

x = range(10)

Call range() With Two Arguments

Example

Create a range of numbers from 3 to 9:

Formula

x = range(3, 10)

Call range() With Three Arguments

Example

Create a range of numbers from 3 to 9:

Formula

x = range(3, 10, 2)

Using ranges

Ranges are often used in for loops to iterate over a sequence of numbers.

Example

Iterate over each value in a range: for i in range(10):

print(i)

Using List to Display Ranges

The range object is a data type that represents an immutable sequence of numbers, and it is not directly displayable. Therefore, ranges are often converted to lists for display.

Example

Convert different ranges to lists:

print(list(range(5)))
print(list(range(1, 6)))
print(list(range(5, 20, 3)))

Slicing Ranges

Like other sequences, ranges can be sliced to extract a subsequence.

Example

Extract a subsequence from a range:

Formula

r = range(10)

print(r[2])
print(r[:3])

Note:

The first print statement returns the value at index 2, and the second print statement returns a new range object, from index 0 to 3.

Membership Testing

Ranges support membership testing with the in operator.

Example

Test if the numbers 6 and 7 are present in a range:

Formula

r = range(0, 10, 2)

print(6 in r)
print(7 in r)

The return value is

True when the number is present in the range, and False when it is not.

Length

Ranges support the len() function to get the number of elements in the range.

Example

Get the length of a range:

Formula

r = range(0, 10, 2)

print(len(r))

Python Generators

Python Arrays