What are python namespaces and scopes? What are its functions?

In this article, let’s take a look at the namespace and scope of the python programming language. In this article we will take a look at python namespaces, and namespaces and scopes. Learn something about them.

Namespace and scope:

A variable is the name (identifier) ​​that holds the matching object. A namespace is a dictionary containing variable names (keys) and their corresponding objects (values).

A Python expression can access variables in the local namespace and global namespace. If a local variable has the same name as a global variable, the local variable overrides the global variable.

Each function has its own namespace. The scoping rules for class methods are the same as for regular functions.

#Python will intelligently guess whether a variable is local or global, assuming that any variable assigned a value within a function is local.

Therefore, if you want to assign a value to a global variable within a function, you must use the global statement.

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
Money = 2000            
def AddMoney():
   # 想改正代码就取消以下注释:
   # global Money
   Money = Money + 1
 
print Money
AddMoney()
print Money

The global VarName expression will tell Python that VarName is a global variable, so that Python will not look for this variable in the local namespace.

For example, we define a variable Money in the global namespace. We then assign a value to the variable Money within the function, and then Python will assume that Money is a local variable. However, we did not declare a local variable Money before accessing it, and the result is an UnboundLocalError. Uncommenting the global statement can solve this problem.

The above is what I want to explain today: namespaces and scopes. Just reading my explanation is just talking on paper. Hands-on practice is the best way to verify what you have learned. Finally, I hope this article can bring some help to you who are learning python.

For more related knowledge, please visit the Python tutorial column on the php Chinese website.

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