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This article mainly explains "the syntax and usage scene of Python3.8 assignment expression". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn the syntax and usage scenario of Python3.8 assignment expression.

The syntax of the assignment expression is "name: = expression", which was once a controversial feature and was eventually added to Python3.8. But it's just an icing on the cake.

We can use an example to understand its usage scenario.

> import re

> data = "hello123world"

> match = re.search ("(\ d +)", data) # 3

> > if match: # 4

... Num = match.group (1)

... Else:

... Num = None

> num

'123'

The code is simple: an operation that uses regular expressions to extract the numeric portion of a string. The previous approach is to first call the re.search method, return the Match object, then assign a value to the variable match, and then determine whether the match object is None to extract the numeric part of it.

In Python3.8, you can combine lines 3 and 4 into one line of code, and in the if statement, you can assign values to variables, which is the assignment expression. There is one less line of code than in the previous version.

> if match:=re.search ((\ d +) ", data):

... Num = match.group (1)

... Else:

... Num = None

...

> num

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