"Life is short, Python is a song."--python Functional Programming 02

Python scope, local and global variables

First understand that Python can change the scope of the code snippet is def class Lamda If/elif/else try/except/finally for/while

The search path for a variable is: local variable-global variable

Try the following code:

x=100def  Main ():    x+=1    print(x) main ()

When running the above code, there will be an error, for what, you need to understand the scope, local variables and the difference between the global variables

x=100def  Main ():    Global  x    x+=1    print(x) main () Print (x)  #全局变量已被改变

Operation Result: 101101

Because we have added global X, the main () function is able to access the global variable x,

Python closures

Here we have a basic understanding of the Python scope rules

Let's write a closure.

# Python 3.5 def Inc ():  #inc是外围函数    x=0    def  Inner ():   #inner is a nested function        nonlocal x        x+=1        print(x)    return  innerinc1=Inc () INC2 =Inc () INC1 () inc1 () inc1 () Inc2 ()

Run Result:1231

From this example, the intrinsic function is returned directly as a return value, where inc1 is a closure, which is essentially a function, consisting of two parts, a inner function and a variable x, and a closure that keeps the values of these variables in memory.

Why use closures?

Closures avoid the use of global variables, and closures can correlate functions with some of the data they manipulate.

"Life is short, Python is a song"--python Functional programming.