day_4_25 py

''' 
Recursion: 
If a function does not call other functions internally, 
but itself, this function is a recursive function 
''' 
def factor(num): 
    if num >1: 
        result = num*factor(num-1 ) 
    else: 
        result =1 
    return result 
ret = factor(3) 
print(ret) 

''' 
Anonymous function: 
Use the lambda keyword to create small anonymous functions. 
This kind of function gets its name from omitting the standard step of declaring a function with def 

lambda [arg1 [,arg2,.....argn]]:expression 
''' #is 
a function without the keyword def 
''' 
anonymous function expansion 
''' 
def fun(a,b,opt): 
    print("a=",a) 
    print("b=",b) 
    print("result=",opt) 
fun(1,2,lambda x,y :



    {"name":"lisi", "age":19}, 
    {"name":"wangwu", "age":17} 
] 
# Sort by name 
stus.sort(key = lambda x:x['name' ]) 
print(stus) 
# Sort by age 
stus.sort(key = lambda x:x['age']) 
print(stus) 
''' 
Exchange of two variables 
''' 
a = 4 
b = 5 
# # The first one 
# c = 0 
# c = a 
# a = b 
# b = c 
# # second 
# a = a+b 
# b = ab 
# a = ab 
# third 
a,b = b,a 
print( "a=%d,b=%d"%(a,b)) 
''' 
document knowledge explanation 
'''