<Python Tips> 3. 迭代与决策

开启Python

➜  ~ docker run --rm -ti python:alpine python
Python 3.7.0 (default, Jul  4 2018, 02:26:27) 
[GCC 6.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

条件编程

>>> late = False
>>> if late:
...     print('I need call my manager')
... else:
...     print('no need to call my manager')
...
no need to call my manager
>>>
>>> if alert_system == 'console':
...     print('console logging')
... elif alert_system == 'email':
...     print('sending email')
... else:
...     print('no logging')
... 
console logging
>>> 

• 三元运算符

>>> can_discount = True
>>> total = 100 if can_discount else 50
>>> total
100
>>> can_discount = False
>>> total = 100 if can_discount else 50
>>> total
50
>>> 

循环

• for

>>> for number in [18, 30, 50]:
...     print(number)
... 
18
30
50
>>> 

• range

>>> list(range(3,8))
[3, 4, 5, 6, 7]

• Sequence

>>> surnames = ['Paul', 'llitfkitfk', 'Tian']
>>> for surname in surnames:
...     print(surname)
... 
Paul
llitfkitfk
Tian
>>> 

• for 循环可以用于lists / tuples等可以迭代的任何类型

>>> people = ['Paul', 'llitfkitfk', 'Tian']
>>> ages = [18, 30, 45]
>>> for person, age in zip(people, ages):
...     print(person, age)
...
Paul 18
llitfkitfk 30
Tian 45

>>>

• while

>>> n = 39
>>> while n > 0:
...     remainder = n % 2
...     remainders.insert(0, remainder)
...     n //= 2
...
>>> print(remainders)
>>>
>>> products = ['car', 'bike', 'truck']
>>> for product in products:
...     if product == 'car':
...             continue
...     print(product)
...
bike
truck
>>>

• break & continue

• 特殊的else

>>> class DriverException(Exception):
...     pass
... 
>>> products = ['car', 'bike', 'truck']
>>> for product in products:
...     if product == 'ship':
...         buy = 'ship'
...         break
... else:
...     raise DriverException('Driver not found')
... 
Traceback (most recent call last):
  File "<stdin>", line 6, in <module>
__main__.DriverException: Driver not found
>>>