Used multiple times , Will call repeatedly
def run(x,y):
print(x,y)
return x,y
run(1,2)
1 Anonymous functions ： It's a function without a name
2 Why use ：
For scenarios that are used only temporarily , There is no need for reuse
Definition of anonymous function
print(lambda x, y: x + y)
expression
(lambda x, y: print(x + y))(1, 2)
Anonymous function general sum max,min,sorted Continuous use
salaries= {
'xialuo':3000000,
'xishi':30000,
'dahai':3000
}
def func(name):
return(salaries[name]
# Compare value value
# For maximum
print(max(salaries,key=lambda name:salaries[name]))
# For the minimum
print(min(salaries,key=lambda name:salaries[name]))
# trans
print(sorted(salaies,key=lambda name:salaries[name],reverse=True))
# positive sequence
print(sorted(salaies,key=lambda name:salaries[name],reverse=False))
1. What is a recursive function
Recursive call of function is a special form of nested call of function , In the process of calling a function, the function itself is called directly or indirectly , Call it a recursive call to a function
Recursive loops are meaningless
Recursive calls must have two explicit phases :
1. to flash back : Call it recursively again and again , To put it bluntly, it is a repeated process ,
However, it should be noted that the scale of each repeated problem should be reduced ,
Until it approaches a final result , That is, the backtracking stage must have a clear end condition
2. Recurrence : Go back layer by layer to calculate the result
Recursion is the calling of nested functions in the definition of a function
***** The difference between recursion and loop , Every time in the cycle, judge , How many times do I have to think about
Recursion only needs to determine the end condition , Repeat the call according to the rule , No need to consider the number of times
The fifth person is the 4 Personal plus 2 year
def age(n):
if n ==1:
return 18
if n>1:
return age(n-1)+2
print(age(5))
Value cycle
L = [1,[2,[3,[4,[5,[6,[7,[8,[9,]]]]]]]]]
def search(L):
for n in L:
# print(n)
if type(n) is not list:
print(' I'm the number %s'%n)
else:
search(n)
search(L)
Closure
Closed means : This function is an internal function
What does Bao mean : It means that the internal function name is referenced externally
def outer(x,y):
def func():
print(x+y)
return func
# The same parameter is passed in every time
func1=outer(3,2)
func1()
func1()
func1()
Decorator is a special closure function
1、 What is a decorator （ It's just a function , But this function is not for your own use , Add functions to other functions ）
A tool is a tool , The function in the program is a tool with a certain function
Decorating refers to adding additional functionality to the decorated object
2、 Why use decorators
Software maintenance should follow the open and closed principle
The open and closed principle refers to ：
Once the software goes online, it is closed to modify the source code , Is open to extended functionality
This uses the decorator
There are two principles to be followed in the realization of decorators ：
1、 Do not modify the source code of the decorated object ( Man's original character , Life style )
2、 Do not modify the call method of the decorated object ( The original appearance of a person , name )
example
name=' The sea '
# Decorator
def decorate(func): #func Wait a minute to pass in run
def new_func(name)：#run(name) Of name
print(" Decorate the front code ")
func(name)
print(" The code behind the decoration ")
return new_func
# Decorated function
def run(name):
print('=================')
print(' I am a %s' %name)
# Run the decorator
@decorate Equivalent to run = decorate(run)
run = decorate(run)
run(name)
