2018-07-29

问题描述：

判断是否是字符串 然后将大写改为小写：

自己代码：

#-*-coding:utf-8-*-

... L1 = {'Hello','World',18,'Apple',None}

>>> [x for x in L1 if isinstance(x,str)]

['Hello', 'Apple', 'World']

>>> L2 = [x for x in L1 if isinstance(x,str)]

>>> [x.lower() for x in L2]

['hello', 'apple', 'world']

别人参考代码：

L2 = [s.lower() for s in L1 if isinstance(s, str)]

>>> print(L2)

['hello', 'apple', 'world']

---

#!/usr/bin/env python3

# -*- coding: utf-8 -*-

from collections import Iterable, Iterator

def g():

    yield 1

    yield 2

    yield 3

print('Iterable? [1, 2, 3]:', isinstance([1, 2, 3], Iterable))

print('Iterable? \'abc\':', isinstance('abc', Iterable))

print('Iterable? 123:', isinstance(123, Iterable))

print('Iterable? g():', isinstance(g(), Iterable))

print('Iterator? [1, 2, 3]:', isinstance([1, 2, 3], Iterator))

print('Iterator? iter([1, 2, 3]):', isinstance(iter([1, 2, 3]), Iterator))

print('Iterator? \'abc\':', isinstance('abc', Iterator))

print('Iterator? 123:', isinstance(123, Iterator))

print('Iterator? g():', isinstance(g(), Iterator))

# iter list:

print('for x in [1, 2, 3, 4, 5]:')

for x in [1, 2, 3, 4, 5]:

    print(x)

print('for x in iter([1, 2, 3, 4, 5]):')

for x in iter([1, 2, 3, 4, 5]):

    print(x)

print('next():')

it = iter([1, 2, 3, 4, 5])

print(next(it))

print(next(it))

print(next(it))

print(next(it))

print(next(it))

d = {'a': 1, 'b': 2, 'c': 3}

# iter each key:

print('iter key:', d)

for k in d.keys():

    print('key:', k)

# iter each value:

print('iter value:', d)

for v in d.values():

    print('value:', v)

# iter both key and value:

print('iter item:', d)

for k, v in d.items():

    print('item:', k, v)

# iter list with index:

print('iter enumerate([\'A\', \'B\', \'C\']')

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

    print(i, value)

# iter complex list:

print('iter [(1, 1), (2, 4), (3, 9)]:')

for x, y in [(1, 1), (2, 4), (3, 9)]:

    print(x, y)