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Function parameters (1)
Think about a question as follows:
Now we need to define a function that can complete the addition of two numbers and print out the result. How should we design it? Is the code below ok? Are there any flaws?
def add2num():
a = 11
b = 22
c = a+b
print(c)
In order to make a function more general, that is, let it calculate the sum of the two numbers that you want it to calculate. When defining the function, you can let the function receive data, which solves this problem. This is the function parameters
1. Define and call a function with parameters
Define a add2num(a, b) function to calculate the sum of any two numbers:
def add2num(a, b):
c = a+b
print(c)
add2num(11, 22) # 调用带有参数的函数时，需要在小括号中，传递数据
important point:
- When defining a function, write the name of the variable waiting to be assigned in parentheses
- When calling the function, write the actual data to be calculated in parentheses
Call the run procedure with a parameter function:
Second, practice
Requirements: Define a function to complete the addition of the first two numbers, and then subtract the third number; then call this function
When using def to define a function, pay attention to the fact that there are 3 parameters
. When calling, this function has several parameters when it is defined, so you need to pass several parameters
3. The order of parameters when calling a function
def test(a,b):
print(a,b)
test(1,2) # 位置参数
test(b=1,a=2) # 关键字参数
test(b=1,2) # 关键字参数写在位置参数之前会导致出错
4. Summary
- Parameters in parentheses when defined are used to receive parameters and are called "formal parameters"
- The parameters in parentheses when calling are used to pass to the function, called "actual parameters"
Function return value (1)
1. Introduction to "return value"
Scenarios in real life:
I gave my son 10 yuan to buy me an ice cream. In this example, I gave 10 yuan to my son, which is equivalent to passing the parameter when calling the function. The ultimate goal of letting my son buy ice cream is that I need to let him bring the ice cream back. At this time, the ice cream is the return value.
Scenario in development:
A function is defined, and the indoor temperature is obtained. Think about whether this result should be given to the caller. Only when the caller has this return value can the appropriate adjustment be made according to the current temperature.
In summary:
The so-called "return value" is the final result to the caller after the function in the program completes one thing. The
prerequisite for using the return value is that the function caller wants to use the calculation result outside the function.
2. Functions with return values
If you want to return the result to the caller in the function, you need to use return in the function
For example:
def add2num(a, b):
c = a+b
return c # return 后可以写变量名
或者
def add2num(a, b):
return a+b # return 后可以写计算表达式
3. Save the return value of the function
At the beginning of this section, in the example of "buying ice cream" mentioned above, when your son gave you ice cream at the end, you must have taken it from your son, right? The same is true for programs. If a function returns a piece of data, then If you want to use this data, you need to save
An example of the return value of the save function is 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
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