What is a slice in python? (Example analysis)

In the following article, let’s learn about what is a slice in python. Learn what slice means in python, and what role slice can play in python.

Getting some elements of a list or tuple is a very common operation in python programming. For example, a list is as follows:

>>> L = ['Michael', 'Sarah', 'Tracy', 'Bob', 'Jack']

How to take the first 3 elements?

Stupid way:

>>> [L[0], L[1], L[2]]
['Michael', 'Sarah', 'Tracy']

For this kind of operation that often takes a specified index range, it is very cumbersome to use a loop. Therefore, Python provides the Slice operator, This operation can be greatly simplified.

Corresponding to the above problem, take the first 3 elements and use one line of code to complete Slicing :

>>> L[0:3]
['Michael', 'Sarah', 'Tracy']

(L[0:3] represents, Take from index 0 until index 3, but not including index 3. That is, index 0, 1, 2, exactly 3 elements.)

If the first index is 0, also Can be omitted:

>>> L[:3]
['Michael', 'Sarah', 'Tracy']

Similarly, since Python supports L[-1] to take the first element from the last, it also supports reciprocal slicing, try:

>>> L[-2:]['Bob', 'Jack']
>>> L[-2:-1]['Bob']

tuple is also a kind of list, the only difference is that tuple is immutable. Therefore, tuples can also be operated by slicing, but the result of the operation is still a tuple:

>>> (0, 1, 2, 3, 4, 5)[:3]
(0, 1, 2)

The string 'xxx' can also be regarded as a list, and each element is a character. Therefore, strings can also be sliced, but the result of the operation is still a string:

>>> 'ABCDEFG'[:3]
'ABC'
>>> 'ABCDEFG'[::2]
'ACEG'

In many programming languages, many interception functions (for example, substring) are provided for strings. In fact, the purpose is Slice the string . Python does not have an interception function for strings. It only requires one operation of slicing, which is very simple.

The above is all the content described in this article. This article mainly introduces the knowledge related to slicing in python. I hope you can use the information to understand the above content. . I hope what I have described in this article will be helpful to you and make it easier for you to learn python.

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