0 introduction and overloading of basic python-modules

Knowledge Points:

1. A xxx.py is a module

2. Import the module is to read the contents of this file

3. The module is the core concept of Python, and large python programs are stacked with multiple modules, just like Lego bricks

Next, I'll put the demo code

Import Sysprint (sys.platform) # System platform Print (2**100) x= "Hello World \ n" Print (x*8) #打印8次temp =input ("Please enter") If temp==8:    Print ("Good luck") Else: print ("    bad Luck") print ("End")    

By running the above code, we will explain the following points of attention

Note the point:

1.import after + file name, without adding. py

2. File name note Do not bring "-", because sometimes do not pay attention to take it, otherwise there will be the following situation

As you can see, we can execute the python-ch3-001.py directly through the instructions, but in Python, it's not going through import.

Below, we copy python-ch3-001.py, named pythonch3001.py, that is, remove the middle "-", we look at the results

From the can see, the same code, different names, in the process of running a very different results, so we need to pay attention to the problem of naming

3. Import the same module, the first time the code is all running, the second time a lot of code is not running, in fact, the middle is just repeated execution

The Middle white box is where the second import is.

At the same time, we tried to modify the source file after the first import, and then import it the second time, the result is the same as the first one.

The reason is that the cost of the import operation is very large, it compiles the file into a byte code, and then the PVM to execute, in the process of compiling, consumes a lot of resources, so, the import operation is only compiled once, the second is only repeated execution, no longer compile

If you want to execute the complete code again, you need to reload () This function, he will reload the source code, and then execute it again, but before executing reload, must ensure that the module has been import

Also, execute the From IMP import reload before executing the reload, because reload is no longer a built-in function in Python3.

From can see, the first time reload, error, then import module, again reload only success

And there will be a print statement prompt after success

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0 introduction and overloading of basic python-modules