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This article introduces the relevant knowledge of "what are the basic knowledge of python3.7 functions?" in the operation of actual cases, many people will encounter such a dilemma, and then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

I. function

I have been in contact with functions since I first came into contact with python. For example, the input () function is used to get the user's keyboard input, the print () function is used to output the results, the range () function is used to generate a sequence of integers, and the len () function is used to obtain the length of the sequence. Not only that, python also provides us with custom functions. Regular, reusable code is about to be encapsulated into functions, thus achieving the result of writing multiple calls at a time. It can be seen that we can simply think of a function as a block of code that can achieve specific functions.

Second, the definition of function

If we ask for the sum between 0 and 100, how should we write it as a function?

Def sun ():

A = 0

For i in list (range):

A + = I

Print (a)

Sun ()

-

5050

In the above code, we define a function to achieve the sum of 0-100. And accurate results are obtained. First use the def keyword to define a function. Followed by a function name. As the name implies, the function name is the name of the function. This name is customized by us and also follows the naming convention. The "()" after the function name indicates a list of parameters. The details will be covered in the next column. What follows the parentheses is the function body, which is our summation function. The last line of the program, sun (), is called a function call. Defines that if the function is not called, it is equivalent to not executing. In short, it is impossible to generate the function of summation.

At the same time, we think about another question. I thought it was said that functions can be reused. It is obvious that the above functions can only complete the summation of 0-100. If you want to complete the sum between 1-1000, or 0-300, do you want to continue to write? Apparently not.

Def sun (mag):

A = 0

For i in list (range (mag)):

A + = I

Print (a)

Sun (1002)

Sun (301)

501501

-

45150

Through the above code we find that we are in the parameter list on the basis of example 1. If mag, this becomes a parameter. I'll talk more about the parameters later. A parameter can have more than one parameter. Parameters are separated by commas. At the same time, we changed the original 100 in range to our parameters. At this point, it is not difficult to find that we put 1001 and 301 in parentheses when calling the function. In this way, the functions of 0-1000 and 0-300 are realized.

So we have new questions. Let's say we not only have to achieve peace. Then we have to get the solution and participate in other operations. What should we do at this time?

Def sun (mag):

A = 0

For i in list (range (mag)):

A + = I

Return a

B = sun (1002)

Print (b)

C = b-10000

Print (c)

501501

-

491501

We added return a to example 2 to mean to return the result of the calculation to the place where the function was called. So we can use a calculation to do something else.

Summary:

Function name: in fact, it is an identifier that conforms to the Python syntax, but readers are not recommended to use simple identifiers such as a, b, c as the function name, the function name had better reflect the function of the function.

Formal parameter list: that is, the list of functions in parentheses above, which sets how many parameters the function can accept, separated by commas (,).

[return [return value]]: as an optional parameter of the function, the whole is used to set the return value of the function. That is to say, a function can return a value or not, depending on the actual situation.

Third, the call of function

So far, I am familiar with function calls. That is, the function name (formal parameter value), and the function name refers to the name of the function to be called; the formal parameter value refers to the value of each parameter that is required to be passed in when the function is created. It is important to note how many formal parameters there are when creating the function. Then how many values need to be passed in when calling, and the order must be the same as when creating the function. Even if the function has no arguments, the parentheses after the function name cannot be omitted.

IV. Pass statement

If you want to define an empty function that does nothing, you can use the pass. pass statement to do nothing, what's the use? In fact, pass can be used as a placeholder. For example, if you haven't figured out how to write the code for a function, you can put a pass to get the code running.

Def sun ():

Pass

Add documentation to the function

Functions are not just for your own use. In a team, it's likely that other people will use it, too. At this point, if he doesn't know the function of the function, he can't call it accurately. Or after a long time to do maintenance and modification, or new employees to take over the project. It's not only inefficient if you don't write notes. And it is possible to become the object of complaint. Therefore, it is necessary to add documentation. For example

""

Function: find the sum of the specified sequence

The maximum value of the sequence to be generated by mag

""

Def sun (mag):

A = 0

# Sum and return the result through loop

For i in list (range (mag)):

A + = I

Return a

B = sun (1002)

Print (b)

VI. Parameter check

If the number of parameters is not correct when the function is called. Python's interpreter will automatically check it out.

""

Function: find the sum of the specified sequence

The maximum value of the sequence to be generated by mag

""

Def sun (mag):

A = 0

# Sum and return the result through loop

For i in list (range (mag)):

A + = I

Return a

B = sun ()

Print (b)

Traceback (most recent call last):

File "/ Users/apple/Documents/ important files / python3/python20.py", line 12, in

B = sun ()

TypeError: sun () missing 1 required positional argument: 'mag'

But the interpreter is powerless if the parameter is not of the right type.

Def my_list (number):

Print (list (range (number)

My_list ("10")

Traceback (most recent call last):

File "/ Users/apple/Documents/ important files / python3/python20.py", line 5, in

My_list ("10") Zhengzhou regular abortion Hospital www.zykdrl120.com

File "/ Users/apple/Documents/ important files / python3/python20.py", line 3, in my_list

Print (list (range (number)

TypeError: 'str' object cannot be interpreted as an integer

Obviously we are going to generate a list of 0-9. However, when we pass in a string, we will report an error. At this point, the built-in function isinstance () comes in handy.

Def my_list (number):

If isinstance (number, int):

Print (list (range (number)

Else:

Print ("only accept integer values")

My_list ("10")

My_list (10)

Only integer values are accepted

-

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Is it possible for one parameter to satisfy two or more types? Yes, of course

Def my_list (number):

If isinstance (number, (int, float, str):

Print ("I met the conditions")

Else:

Print ("I don't meet the conditions")

My_list ("10")

My_list (10)

My_list ((1,2))

I met the conditions.

I met the conditions.

I don't meet the conditions.

7. The function returns multiple values

Def my_list ():

Return 10, 20, [1, 3]

A = my_list ()

Print (a)

(10, 20, [1,3])

From the above example, we can know that the function can return multiple values at one time. But this return value is tuple

This is the end of the introduction of "what are the basics of python3.7 functions". Thank you for your reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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