Python高阶函数、常用内置函数用法实例分析

#返回值为函数的函数
sum=lambda x,y:x+y
sub=lambda x,y:x-y
calc_dict={"+":sum,"-":sub}
def calc(x):
  return calc_dict[x]

print(calc('-')(5,6))
print(calc('+')(5,6))

#参数有函数的函数
filter(lambda x:x>5,range(20))

>>> print(range(20))
range(0, 20)
>>> type(range(20))
<class 'range'>
>>> isinstance(range(20),Iterable)#########是一个可迭代对象
True
>>> from collections import Iterator
>>> isinstance(range(20),Iterator)#不是一个迭代器对象
False

>>> oct(8)
'0o10'
>>> hex(8)
'0x8'
>>> bin(8)
'0b1000'

>>> ord('中')
20013
>>> chr(20013)
'中'

for i, value in enumerate(['A', 'B', 'C']):
  print(i, value)

from collections import Iterator
#可以被next()函数调用并不断返回下一个值的对象称为迭代器：Iterator。
print(isinstance([],Iterator))
print(isinstance(iter([]),Iterator))

>>> l=[8,7,6,5,4,3,2,1]
>>> sorted(l)
[1, 2, 3, 4, 5, 6, 7, 8]

>>> l=[]
>>> all(l)
True
>>> l=[1,2,3,4,5]
>>> all(l)
True
>>> l=[1,2,3,4,5,0]
>>> all(l)
False

>>> l=[]
>>> any(l)
False
>>> l=[0,0,0,0]
>>> any(l)
False
>>> l=[0,0,0,0,5]
>>> any(l)
True
>>>

>>> str1="3+4"
>>> eval(str1)
7

>>> str1="print('hello world')"
>>> exec(str1)
hello world

str1 = "print('hello world')"
c2 = compile(str1,'','exec')  
exec(c2)

str2="3+4"
c3=compile(str2,'','eval')
a=eval(c3)
print(a)

>>> id(str1)
1514678732384
>>> str2=str1
>>> id(str2)
1514678732384

>>> isinstance(1,int)
True
>>> isinstance(1.0,int)
False

>>> a=b'abc'
>>> len(a)
3
>>> b="我爱中国"
>>> len(b)
4
>>> c=[1,2,3,4]
>>> len(c)
4

>>> c=[1,2,3,4]
>>> repr(c)
'[1, 2, 3, 4]'
>>> d={1:2,2:3,3:4}
>>> repr(d)
'{1: 2, 2: 3, 3: 4}'

>>> type(1)
<class 'int'>
>>> type("123")
<class 'str'>
>>> type((1,2,3))
<class 'tuple'>