70 lines
1.3 KiB
Markdown
70 lines
1.3 KiB
Markdown
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### dict 遍历
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- 关键字和对应的值可以使用 items() 方法同时解读出来
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```python
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>>> knights = {'gallahad': 'the pure', 'robin': 'the brave'}
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>>> for k, v in knights.items():
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... print(k, v)
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...
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gallahad the pure
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robin the brave
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```
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### 序列遍历
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- 索引位置和对应值可以使用 enumerate() 函数同时得到
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```python
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>>> for i, v in enumerate(['tic', 'tac', 'toe']):
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... print(i, v)
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...
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0 tic
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1 tac
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2 toe
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```
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- 同时遍历两个或更多的序列，可以使用 zip() 组合，迭代器性质，遍历一遍后清空，无法再次遍历
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```python
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>>> questions = ['name', 'quest', 'favorite color']
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>>> answers = ['lancelot', 'the holy grail', 'blue']
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>>> for q, a in zip(questions, answers):
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... print('What is your {0}? It is {1}.'.format(q, a))
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...
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What is your name? It is lancelot.
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What is your quest? It is the holy grail.
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What is your favorite color? It is blue.
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```
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- 反向遍历一个序列，首先指定这个序列，然后调用 reversed()
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```python
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>>> for i in reversed(range(1, 10, 2)):
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... print(i)
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...
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9
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7
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5
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3
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1
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```
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- 按顺序遍历一个序列，使用 sorted() 函数返回一个已排序的序列，并不修改原值
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```python
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>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
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>>> for f in sorted(set(basket)):
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... print(f)
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...
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apple
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banana
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orange
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pear
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```
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