Example analysis of Python function local variable usage

The example in this article describes the Python function local variable usage. Share to everyone for your reference. The specific analysis is as follows:

When you declare variables within a function definition, they are not related to other variables with the same name outside the function, that is, the variable name is local to the function. This is called the scope of the variable. All variables are scoped to their defined blocks, starting with the point where their names are defined.

First, using local variables

Examples are as follows:

#!/usr/bin/python# Filename:func_local.pydef func (x):  print ' x is ', x  x = 2 "  print ' Changed local x to ', XX = 50func (x) print ' x is still ', X

Output:

$ python Func_local.pyx is 50Changed local x to 2x is still 50

Working principle:

In the function, the first time we use the value of X, Python uses the value of the formal parameter declared by the function.
Next, we assign the value 2 to X. X is the local variable of the function. So, when we change the value of x within a function, the x defined in the main block is unaffected.
In the last print statement, we proved that the value of x in the main block was not really affected.

Second, use the global statement

If you want to assign a value to a variable that is defined outside the function, then you have to tell Python that the variable name is not local, but global. We use the global statement to complete this function. Without the global statement, it is impossible to assign a value to a variable that is defined outside the function.

You can use the values of variables defined outside the function (assuming there are no variables with the same name within the function). However, I do not encourage you to do so, and you should try to avoid doing so, as this makes the reader of the program unclear where the variable is defined. Using the global statement makes it clear that the variable is defined outside the block.

Use the Global Statement example:

#!/usr/bin/python# Filename:func_global.pydef func ():  Global x  print ' x is ', x  x = 2  print ' Changed loca L x to ', XX = 50func () print ' Value of X ', X

Output:

$ python Func_global.pyx is 50Changed Global X to 2Value of X is 2

Working principle:

The global statement is used to declare that X is global-so when we assign a value to x within a function, the change is reflected when we use the value of x in the main block.
You can use the same global statement to specify multiple global variables. For example, Global x, Y, Z.

Hopefully this article will help you with Python programming.

