Array slicing gets a subset of an array

Array slicing is a simple way to obtain a subset of an array. The syntax is array[start:stop:step]. By specifying the index range and step size, you can get the required elements. For example, array[2:6] gets elements from index 2 to 6 (exclusive), array[::-1] reverses the array.

Array slicing: Obtaining a subset of an array

Array slicing is a convenient way to obtain a subset of an array in Python . It allows you to specify elements to include or exclude from an array using a concise syntax.

Syntax

Array slicing uses square brackets ([]), followed by a colon (:) to separate index ranges:

array[start:stop:step]

• start: Specifies the index at which the slice starts (inclusive).
• stop: Specifies the index at which the slice ends (not included).
• step: Specify the slicing step (optional). It specifies how many elements to skip.

Practical case

The following example demonstrates how to use array slicing to obtain a subset of an array:

# 创建一个数组
array = [1, 2, 3, 4, 5, 6, 7, 8, 9]

# 获取数组的前 4 个元素
sub_array1 = array[:4]
print(sub_array1)  # 输出：[1, 2, 3, 4]

# 获取数组中索引 2 到 6（不包含）的元素
sub_array2 = array[2:6]
print(sub_array2)  # 输出：[3, 4, 5, 6]

# 获取以步长 2 递增的数组元素
sub_array3 = array[::2]  # 等同于 array[0:len(array):2]
print(sub_array3)  # 输出：[1, 3, 5, 7, 9]

# 反转数组
sub_array4 = array[::-1]
print(sub_array4)  # 输出：[9, 8, 7, 6, 5, 4, 3, 2, 1]

Some points to note

• Indices start from 0.
• If start or stop are omitted, it will be interpreted as the beginning or end of the array.
• step Default is 1.
• If start is greater than stop, the slice will be empty.
• Slicing returns a new array, which is independent of the original array.

The above is the detailed content of Array slicing gets a subset of an array. For more information, please follow other related articles on the PHP Chinese website!