python高级特性简介

L = list(range(100))

#利用切片取部分元素
print(L[0:10]) #取从索引从0到9的前10个元素
print(L[-10:]) #取最后10个元素
print(L[10:20])#取从索引10到19的10个元素
print(L[:10:2])#从前10个元素中每两个取一个元素
print(L[::10]) #所有元素中每10个取一个元素 

from collections import Iterable

print('字符串 is Iterable ?',isinstance('abc',Iterable))
print('list is Iterable ?',isinstance([1,2,3],Iterable))
print('整数 is Iterable ?',isinstance(123,Iterable))

#遍历字符串:
for ch in 'abc':
  print(ch)

#遍历list
L = ['A','B','C']
for tmp in L:
  print(tmp)

for i,value in enumerate(L):
  print(i,':',value)

#遍历dict
d = {'1':'111','2':'222','3':'333'}
for key,v in d.items():
  print('key:',key,'value:',v)

list(range(1, 11))

[x * x for x in range(1,11)]

#[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

[x * x for x in range(1, 11) if x % 2 == 0]

[4, 16, 36, 64, 100]

[m + n for m in 'ABC' for n in 'XYZ']

['AX', 'AY', 'AZ', 'BX', 'BY', 'BZ', 'CX', 'CY', 'CZ']

L = [x * x for x in range(1,10)]
print(L)

g = (x * x for x in range(1,10))
print(g)

//运行结果：
[1, 4, 9, 16, 25, 36, 49, 64, 81]
<generator object <genexpr> at 0x10cc14938>

def fib(max):
  n,a,b = 0,0,1
  while n < max:
    yield b
    a,b = b, a+b
    n = n + 1
  return 'done' 

print(fib(6))

from collections import Iterator
print('list is Iterator ?',isinstance([], Iterator))
print('dict is Iterator ?',isinstance({}, Iterator))
print('string is Iterator ?',isinstance('123', Iterator))

//运行结果:
list is Iterator ? False
dict is Iterator ? False
string is Iterator ? False