Python的Lambda函数用法详解

def sq(x): 
  return x*x 
 
map(sq,[y for y in range(10)]) 

a,b 
a=1,b=2 
*args 
**kwargs 
a,b=1,*args 
空 
.... 

1 
None 
a+b 
sum(a) 
1 if a >10 else 0 
...... 

import time 
 
 
# 测试的Def函数 
def square1(n): 
  return n ** 2 
 
 
# 测试的Lambda函数 
square2 = lambda n: n ** 2 
 
print(time.time()) 
 
# 使用Def函数 
i = 0 
while i < 1000000000: 
  square1(100) 
  i += 1 
 
print(time.time()) 
 
# 使用lambda函数 
i = 0 
while i < 1000000000: 
  square2(100) 
  i += 1 
 
print(time.time()) 
 
1413272496.27 
1413272703.05 (Def  函数:207s) 
1413272904.49 (Lambda函数:201s) 

c=lambda x,y,z:x*y*z 
c(2,3,4) 
 
24 

(lambda x:x**2)(3) 
9 

fliter(lambda x:x%3==0,[1,2,3,4,5,6]) 
[3,6] 
squares = map(lambda x:x**2,range(5) 
print(lsit(squares)) 
[0,1,4,9,16] 

sorted(a,key=lambda x:x[0]) 
[('a',2),('b',3),('c',1),('d',4)] 

sorted(a,key=lambda x:x[1]) 
[('c',1),('a',2),('b',3),('d',4)] 

from functools import reduce 
print(reduce(lambda a,b:'{},{}'.format(a,b),[1,2,3,4,5,6,7,8,9])) 
1,2,3,4,5,6,7,8,9 

def increment(n): 
  return lambda x:x+n 
 
f=increment(4) 
f(2) 
6 

x=(lambda x='Boo',y='Too',z='Z00'：x+y+z) 
print(x('Foo')) 
 
'FooTooZoo' 

import sys 
from tkinter import Button,mainloop 
 
x=Button(text='Press me',command=(lambda :sys.stdout.write('Hello,World\n'))) 
x.pack() 
x.mainloop() 

Names = ['Anne', 'Amy', 'Bob', 'David', 'Carrie', 'Barbara', 'Zach'] 
B_Name= filter(lambda x: x.startswith('B'),Names) 
print(B_Name) 
['Bob', 'Barbara'] 

a = [1,2,3,4] 
b = [5,6,7,8] 
print(list(map(lambda x,y:x+y, a,b))) 
[6,8,10,12] 

sentence = "Welcome To Beijing!" 
words = sentence.split() 
lengths = map(lambda x:len(x),words) 
print(list(lengths)) 
[7,2,8]