Code analysis of return values ​​and types of functions in python

1. Return value introduction

Real life scenario:

I gave my son 10 yuan and asked him to buy it for me Pack of cigarettes. In this example, I gave 10 yuan to my son, which is equivalent to passing the parameters when calling the function. The ultimate goal of letting my son buy cigarettes is to let him bring the cigarettes back to you and then give them to you, right? At this time, the smoke is the return value

Scenario in development:

defines a function and completes the acquisition of indoor temperature. Think about whether this result should be given to the caller, only the caller Only with this return value can we make appropriate adjustments according to the current temperature

In summary:

The so-called "return value" means that after the function in the program completes one thing, the final Result to the caller

2. Function with return value

If you want to return the result to the caller in the function, you need to use return

in the function as follows Example:

def add2num(a, b):
	c = a+b
    return c

or

def add2num(a, b):
    return a+b

3. Save the return value of the function

In the example of "buying cigarettes" mentioned at the beginning of this section, at the end When your son gives you a cigarette, you must take it from his hand, right? The same is true for programs. If a function returns a data, and you want to use this data, you need to save the return of the function. Value examples are as follows:

#定义函数
def add2num(a, b):
	return a+b
#调用函数，顺便保存函数的返回值
result = add2num(100,98)
#因为result已经保存了add2num的返回值，所以接下来就可以使用了
print (result)

Result:

198

4. Types of four functions

Functions depend on whether they have parameters or not , whether there is a return value, can be combined with each other, there are 4 types in total

No parameters, no return value
No parameters, regret again
There are parameters and no return value
There are parameters and there are return values
1.None Parameters, functions without return values

This type of function cannot receive parameters and has no return value. Generally, it has a function similar to the printing prompt light. Use this type of function

def printMenu():
    print('--------------------------')
    print('      xx涮涮锅 点菜系统')
    print('')
    print('  1.  羊肉涮涮锅')
    print('  2.  牛肉涮涮锅')
    print('  3.  猪肉涮涮锅')
    print('--------------------------')

The result :

2. Functions with no parameters and return values

This type of function cannot receive parameters, but can return certain data. Under normal circumstances , like collecting data, use this type of function

# 获取温度
def getTemperature():
    #这里是获取温度的一些处理过程
    #为了简单起见，先模拟返回一个数据
	return 24
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temperature = getTemperature()
print('当前的温度为:%d'%temperature)

Result:

The current temperature is: 24

3. There are parameters, but no return value Function

This type of function can receive parameters, but cannot return data. Generally, this type of function is used when setting data for certain variables without requiring results

4. Functions with parameters and return values

This type of function can not only receive parameters, but also return certain data. Generally speaking, such functions are used for applications that require data processing and require results

 # 计算1~num的累积和
def calculateNum(num):
    result = 0
    i = 1
    while i<=num:
        result = result + i
        i+=1
    return result
result = calculateNum(100)
print(&#39;1~100的累积和为:%d&#39;%result)

Result: The cumulative sum of

1~100 is: 5050

5. Summary

The function depends on whether there are parameters or not. When the return values ​​can be combined with each other to define functions, they are designed based on actual functional requirements, so the function types written by different developers are different

5. Can we return multiple values ​​in python?

>>> def divid(a, b):
...     shang = a//b
...     yushu = a%b 
...     return shang, yushu
...
>>> sh, yu = divid(5, 2)
>>> sh
5
>>> yu
1

The essence is to use tuples

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