[work] python---lambda、filter、参数的位置/关键字/收集/顺序匹配

男娘i 2022-04-12 11:42 173阅读 0赞

python —lambda

step2:lambda之再议

1.lambda是一个表达式。  
2.它没有名称，存储的也不是代码块，而是表达式。  
3.它被用作执行很小的功能，不能在里面使用条件语句。  
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root@kali:~/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):\#与lambda区别是有return返回  
return x+1  
e(8)  
e(9)

root@kali:~/python/laowangpy/function\# python k501lambda.py  
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root@kali:~/python/laowangpy/function\#  
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在lambda使用if……else…..语句

root@kali:~/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)  
root@kali:~/python/laowangpy/function\# python k501lambda.py  
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root@kali:~/python/laowangpy/function\#  
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在lambda中使用列表推导

root@kali:~/python/laowangpy/function\# cat k501lambda.py  
\#!usr/bin/python  
\# --\*-- coding:utf-8 --\*--

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

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

print g(1)

root@kali:~/python/laowangpy/function\# python k501lambda.py  
\[(1, 0), (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (1, 7), (1, 8), (1, 9)\]  
root@kali:~/python/laowangpy/function\#  
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结合filter使用过滤功能

root@kali:~/python/laowangpy/function\# cat k501lambda.py  
\#!usr/bin/python  
\# --\*-- coding:utf-8 --\*--

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

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

print g(1)  
'''

\#结合filter使用过滤功能（常用过滤、判断、查询条件）  
t = \[2,3,4,5,61,2,34,52,1,1,2,3,7,1\]

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

print h

root@kali:~/python/laowangpy/function\# python k501lambda.py  
\[3, 4, 5, 61, 34, 52, 3, 7\]  
root@kali:~/python/laowangpy/function\#

以上题目的伪代码  
h = \[\]  
for x in t:  
if x>2:  
h.append(x)  
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结合filter使用过滤功能

>>> def shortstr(\*kargs):  
... list = filter(lambda x:isinstance(x,str),kargs)\#判断是否为字符串  
... len\_list = \[len(x) for x in list\]\#对字符串长度判断  
... min\_len = min(len\_list)\#取出最短的字符串  
... return list\[len\_list.index(min\_len)\]\#返回最短的字符串  
...  
>>> print shortstr(22,334,"xixi","hahahha","wowowo")  
xixi  
>>>  
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step3:函数参数总结

1.位置匹配 func(name)  
2.关键字匹配 func(key=value)  
3.收集匹配  
1.元组收集 func(name,arg1,arg2)  
2.字典收集 func(name,key1=value1,key1=value2)  
4.参数顺序  
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step4:接触递归

1.递归是调用自身  
2.理解下面的函数  
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位置匹配 func(name)（参数的位置一一对应）  
def func(arg1,arg2,arg3):  
return arg1,arg2,arg3

print func(1,2,3)

关键字匹配 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.元组收集 func(name,arg1,arg2)  
2.字典收集 func(name,key1=value1,key1=value2)

\* kargs 元组  
\*\* 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\})  
>>>

参数位置：  
1.先是位置匹配的参数  
2.再是关键字匹配的参数  
3.收集匹配的元组参数  
4.收集匹配的关键字参数  
>>> 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：徐为波  
来源：CSDN  
原文：https://blog.csdn.net/xwbk12/article/details/78572766  
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