python —lambda

step2:lambda之再議

1.lambda是一個表示式。
2.它沒有名稱，儲存的也不是程式碼塊，而是表示式。
3.它被用作執行很小的功能，不能在裡面使用條件語句。
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[email protected]:~/python/laowangpy/function# cat k501lambda.py 
#!usr/bin/python
# --*-- coding:utf-8 --*--

d = lambda x:x+1

print d(3)
print d(4)

def e(x):#與lambda區別是有return返回
    return x+1
e(8)
e(9)

[email protected]:~/python/laowangpy/function# python k501lambda.py 
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[email protected]:~/python/laowangpy/function# 
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在lambda使用if……else…..語句

[email protected]:~/python/laowangpy/function# cat k501lambda.py 
#!usr/bin/python
# --*-- coding:utf-8 --*--

d = lambda x:x+1 if x>0 else "error"

print d(3)
print d(4)
print d(-2)
[email protected]:~/python/laowangpy/function# python k501lambda.py 
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error
[email protected]:~/python/laowangpy/function# 
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在lambda中使用列表推導

[email protected]:~/python/laowangpy/function# cat k501lambda.py 
#!usr/bin/python
# --*-- coding:utf-8 --*--

'''
使用if....else....語句
d = lambda x:x+1 if x>0 else "error"

print d(3)
print d(4)
print d(-2)
'''
#使用列表推導
g = lambda x:[(x,i) for i in xrange(0,10)]

print g(1)

[email protected]:~/python/laowangpy/function# python k501lambda.py 
[(1, 0), (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (1, 7), (1, 8), (1, 9)]
[email protected]:~/python/laowangpy/function# 
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結合filter使用過濾功能

[email protected]:~/python/laowangpy/function# cat k501lambda.py 
#!usr/bin/python
# --*-- coding:utf-8 --*--

'''
使用if....else....語句
d = lambda x:x+1 if x>0 else "error"

print d(3)
print d(4)
print d(-2)
'''
'''
使用列表推導
g = lambda x:[(x,i) for i in xrange(0,10)]

print g(1)
'''

#結合filter使用過濾功能（常用過濾、判斷、查詢條件）
t = [2,3,4,5,61,2,34,52,1,1,2,3,7,1]

h = filter(lambda x:x>2,t)

print h

[email protected]:~/python/laowangpy/function# python k501lambda.py 
[3, 4, 5, 61, 34, 52, 3, 7]
[email protected]:~/python/laowangpy/function# 

以上題目的虛擬碼
h = []
for x  in t:
    if x>2:
        h.append(x)
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結合filter使用過濾功能

>>> def shortstr(*kargs):
...     list = filter(lambda x:isinstance(x,str),kargs)#判斷是否為字串
...     len_list = [len(x) for x in list]#對字串長度判斷
...     min_len = min(len_list)#取出最短的字串
...     return list[len_list.index(min_len)]#返回最短的字串
... 
>>> print shortstr(22,334,"xixi","hahahha","wowowo")
xixi
>>> 
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step3:函式引數總結

1.位置匹配 func(name)
2.關鍵字匹配 func(key=value)
3.收集匹配
        1.元組收集 func(name,arg1,arg2)
        2.字典收集 func(name,key1=value1,key1=value2)
4.引數順序
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step4:接觸遞迴

1.遞迴是呼叫自身
2.理解下面的函式
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位置匹配 func(name)（引數的位置一一對應）
def func(arg1,arg2,arg3):
    return arg1,arg2,arg3

print func(1,2,3)

關鍵字匹配 func(key=value)
def func1(k1='',k2=None,k3=''):
    return k1,k2,k3

print func1(k3=5,k1=4,k2=3)

收集匹配:1.元組收集 func(name,arg1,arg2)
        2.字典收集 func(name,key1=value1,key1=value2)

* kargs 元組
** kwargs 字典

>>> def fun2(*kargs,**kwargs):
...     return kargs
... 
>>> print fun2(2,3,4,5,6,7,8)
(2, 3, 4, 5, 6, 7, 8)
>>> print fun2(2,3,4,5,6,7,8,[11,22,33,44,55,66],{111:222,333:444,555:666})
(2, 3, 4, 5, 6, 7, 8, [11, 22, 33, 44, 55, 66], {555: 666, 333: 444, 111: 222})
>>> 

引數位置：
1.先是位置匹配的引數
2.再是關鍵字匹配的引數
3.收集匹配的元組引數
4.收集匹配的關鍵字引數
>>> def fun2(*kargs,**kwargs):
...     return kargs
... 
>>> print fun2(2,3,4,5,6,7,8)
(2, 3, 4, 5, 6, 7, 8)
>>> print fun2(2,3,4,5,6,7,8,[11,22,33,44,55,66],{111:222,333:444,555:666})
(2, 3, 4, 5, 6, 7, 8, [11, 22, 33, 44, 55, 66], {555: 666, 333: 444, 111: 222})
>>> 
>>> 
>>> def fun2(a,*kargs,**kwargs):
...     return kargs
... 
>>> print fun2(2,3,4,5,6,7,8,[11,22,33,44,55,66],{111:222,333:444,555:666})
(3, 4, 5, 6, 7, 8, [11, 22, 33, 44, 55, 66], {555: 666, 333: 444, 111: 222})
>>> 
>>> 
>>> def fun2(a,d,b=4,*kargs,**kwargs):
...     return kargs
... 
>>> 
>>> print fun2(2,3,4,5,6,7,8,[11,22,33,44,55,66],{111:222,333:444,555:666})
(5, 6, 7, 8, [11, 22, 33, 44, 55, 66], {555: 666, 333: 444, 111: 222})
>>> 

def func2(a,d,b=4,*kargs,**kwargs):
    return kargs
print func2(2,3,4,5,6,7,9,[1,2,3,4],{1:2,3:4})

# d = lambda x:x+1 if x > 0 else "error"
# g = lambda x:[(x,i) for i in xrange(0,10)]

# def e(x):
#   return x+1

# t = [1,2,3,4,5]
# g = filter(lambda x:x > 3,t)

# print d(2)
# print d(4)
# print d(5)
# print d(-1)
# print d(-2)
# #print g(10)
# print g

def func1(i):
    if i<100:
        return i + func1(i+1)
    return i
print func1(0)
--------------------- 
作者：徐為波 
來源：CSDN 
原文：https://blog.csdn.net/xwbk12/article/details/78572766 
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