Syntax and usage scenarios of Python3.8 assignment expressions
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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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