Python学习笔记

Python简介

Python基础

数据类型和变量

整数

浮点数

字符串

r''

''

'''...'''

布尔值

True

False

and

or

not

空值

None

变量

a = 'abc'

'abc'

a

'ABC'

常量

/

//

%

小结

inf

字符串和编码

字符编码

Python的字符串

ord()

chr()

str

bytes

bytes

x = b'abc'

str

encode()

bytes

'abc'.encode('ascii')

bytes

decode()

str

b'abc'.decode('ascii')

len()

str

bytes

格式化

'hello,%s' % 'world'

'hello,world'

使用list和tuple

list

>>> classmates = ['Michael', 'Bob', 'Tracy']`
>>> classmates
['Michael', 'Bob', 'Tracy']

len()

len(classmates)

0

len(classmates)-1

-1

append()

classmates.append('adam')

insert()

calssmates.insert(1,'jack')

pop()

classmates.pop()

pop(i)

classmates.pop(1)

classmates[1] = 'sarah'

L = []

tuple

>>> classmates = ('Michael', 'Bob', 'Tracy')

t = ()

,

t = (1,)

>>> t = ('a', 'b', ['A', 'B'])
>>> t[2][0] = 'X'
>>> t[2][1] = 'Y'
>>> t
('a', 'b', ['X', 'Y'])

小结

条件判断

条件判断

if

age = 20
if age >= 18:
print('your age is', age)
print('adult')

if-else

if-elif-else

elif

else if

if

if <条件判断1>:
<执行1>
elif <条件判断2>:
<执行2>
elif <条件判断3>:
<执行3>
else:
<执行4>

:

再议input

birth = input('birth: ')

birth

str

int()

s = input('birth: ')
birth = int(s)

循环

names = ['Michael', 'Bob', 'Tracy']
for name in names:
print(name)

sum = 0
n = 99
while n > 0:
sum = sum + n
n = n - 2
print(sum)

使用dict和set

dict

>>> d = {'Michael': 95, 'Bob': 75, 'Tracy': 85}
>>> d['Michael']
95

>>> d['Adam'] = 67
>>> d['Adam'
20000
]
67

in

>>> 'Thomas' in d
False

>>> d.get('Thomas')
>>> d.get('Thomas', -1)
-1

>>> d.pop('Bob')
75

list

set

>>> s = set([1, 2, 3])
>>> s
{1, 2, 3}

add(key)

>>> s.add(4)

>>> s.remove(4)

函数

调用函数

abs()

>>> abs(100)
100
>>> abs(-20)
20
>>> abs(12.34)
12.34

max()

>>> max(1, 2)
2
>>> max(2, 3, 1, -5)
3

数据类型转换

int()

float()

str()

bool()

>>> a = abs # 变量a指向abs函数
>>> a(-1) # 所以也可以通过a调用abs函数
1

定义函数

def my_abs(x):
if x >= 0:
return x
else:
return -x

return

None

return None

return

.py

from 文件名 import 函数名

空函数

pass

def nop():
pass

参数检查

TypeError

返回多个值

小结

函数的参数

位置参数

def power(x):
return x * x

power

def power(x, n):
s = 1
while n > 0:
n = n - 1
s = s * x
return s

power

x

n

默认参数

def power(x, n=2):
s = 1
while n > 0:
n = n - 1
s = s * x
return s

power

power(5)

power(5,3)

可变参数

def calc(*numbers):
sum = 0
for n in numbers:
sum = sum + n * n
return sum

*

numbers

*

>>> nums = [1, 2, 3]
>>> calc(*nums)
14

关键字参数

def person(name, age, **kw):
print('name:', name, 'age:', age, 'other:', kw)

**

>>> extra = {'city': 'Beijing', 'job': 'Engineer'}
>>> person('Jack', 24, **extra)
name: Jack age: 24 other: {'city': 'Beijing', 'job': 'Engineer'}

**extra

extra

**kw

kw

kw

extra

kw

extra

命名关键字参数

def person(name, age, *, city, job):
print(name, age, city, job)

**kw

*

*

>>> person('Jack', 24, city='Beijing', job='Engineer')
Jack 24 Beijing Engineer

参数组合

func(*args, **kw)

小结

*args

**kw

func(1, 2, 3)

*args

func(*(1, 2, 3))

func(a=1, b=2)

**kw

func(**{'a': 1, 'b': 2})

*args

**kw

递归函数

def fact(n):
if n==1:
return 1
return n * fact(n - 1)

def fact(n):
return fact_iter(n, 1)

def fact_iter(num, product):
if num == 1:
return product
return fact_iter(num - 1, num * product)

高级特性

切片

>>> L = ['Michael', 'Sarah', 'Tracy', 'Bob', 'Jack']
>>> L[0:3]
['Michael', 'Sarah', 'Tracy']

L[0:3]

0

3

3

0

L[:3]

>>> L[-2:]
['Bob', 'Jack']
>>> L[-2:-1]
['Bob']

L[:10:2]

[:]

>>> L = list(range(100))
>>> L
[0, 1, 2, 3, ..., 99]

>>> L[:10]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> L[-10:]
[90, 91, 92, 93, 94, 95, 96, 97, 98, 99]

>>> L[10:20]
[10, 11, 12, 13, 14, 15, 16, 17, 18, 19]

>>> L[::5]
[0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95]

>>> L[:]
[0, 1, 2, 3, ..., 99]

>>> L[::-1]
[99, 98, 97, 96, ..., 0]

小结

迭代

for...in

>>> d = {'a': 1, 'b': 2, 'c': 3}
>>> for key in d:
...     print(key)
...
a
c
b

for value in d.value

for k, v in d.iterms()

for

for

>>> from collections import Iterable
>>> isinstance('abc', Iterable) # str是否可迭代
True
>>> isinstance([1,2,3], Iterable) # list是否可迭代
True
>>> isinstance(123, Iterable) # 整数是否可迭代
False

enumerate

for

>>> for i, value in enumerate(['A', 'B', 'C']):
...     print(i, value)
...
0 A
1 B
2 C

小结

列表生成式

>>> [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']

>>> d = {'x': 'A', 'y': 'B', 'z': 'C' }
>>> [k + '=' + v for k, v in d.items()]
['y=B', 'x=A', 'z=C']

os.listdir()

小结

生成器

[]

()

>>> L = [x * x for x in range(10)]
>>> L
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
>>> g = (x * x for x in range(10))
>>> g
<generator object <genexpr> at 0x1022ef630>

next()

>>> next(g)
0
>>> next(g)
1
>>> next(g)
4
>>> next(g)
9

for

>>> g = (x * x for x in range(10))
>>> for n in g:
...     print(n)
...
0
1
4
9
16
25
36
49
64
81

yield

return

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

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

>>> f = fib(6)
>>> f
<generator object fib at 0x104feaaa0>

小结

>>> r = abs(6)
>>> r
6

>>> g = fib(6)
>>> g
<generator object fib at 0x1022ef948>

迭代器

for

list

tuple

dict

set

str

yield

Iterable

isinstance()

>>> from collections import Iterable
>>> isinstance([], Iterable)
True
>>> isinstance({}, Iterable)
True
>>> isinstance('abc', Iterable)
True
>>> isinstance((x for x in range(10)), Iterable)
True
>>> isinstance(100, Iterable)
False

next()

Iterator

isinstance()

>>> from collections import Iterator
>>> isinstance((x for x in range(10)), Iterator)
True
>>> isinstance([], Iterator)
False
>>> isinstance({}, Iterator)
False
>>> isinstance('abc', Iterator)
False

Iterator

list

dict

str

Iterable

Iterator

iter()

Iterable

Iterator

>>> isinstance(iter([]), Iterator)
True
>>> isinstance(iter('abc'), Iterator)
True

Iterator

next()

Iterator

Iterator

小结

for

Iterable

next()

Iterator

list

dict

str

Iterable

Iterator

iter()

Iterator

for

next()

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

# 首先获得Iterator对象:
it = iter([1, 2, 3, 4, 5])
# 循环:
while True:
try:
# 获得下一个值:
x = next(it)
except StopIteration:
# 遇到StopIteration就退出循环
break

函数式编程

高阶函数

小结

map / reduce

map()

reduce()

map()

Iterable

map

Iterator

>>> def f(x):
...     return x * x
...
>>> r = map(f, [1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> list(r)
[1, 4, 9, 16, 25, 36, 49, 64, 81]

>>> list(map(str, [1, 2, 3, 4, 5, 6, 7, 8, 9]))
['1', '2', '3', '4', '5', '6', '7', '8', '9']

reduce()

reduce

reduce

sum（）

>>> from functools import reduce
>>> def add(x, y):
...     return x + y
...
>>> reduce(add, [1, 3, 5, 7, 9])
25

str2int

from functools import reduce

def str2int(s):
def fn(x, y):
return x * 10 + y
def char2num(s):
return {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}[s]
return reduce(fn, map(char2num, s))

filter

filter()

filter()

def is_odd(n):
return n % 2 == 1

list(filter(is_odd, [1, 2, 4, 5, 6, 9, 10, 15]))
# 结果: [1, 5, 9, 15]

def not_empty(s):
return s and s.strip()

list(filter(not_empty, ['A', '', 'B', None, 'C', '  ']))
# 结果: ['A', 'B', 'C']

def _odd_iter():
n = 1
while True:
n = n + 2
yield n

def _not_divisible(n):
return lambda x: x % n > 0

def primes():
yield 2
it = _odd_iter() # 初始序列
while True:
n = next(it) # 返回序列的第一个数
yield n
it = filter(_not_divisible(n), it) # 构造新序列

# 打印1000以内的素数:
for n in primes():
if n < 1000:
print(n)
else:
break

小结

sorted

>>> sorted([36, 5, -12, 9, -21], key=abs)
[5, 9, -12, -21, 36]

sorted()

>>> sorted([36, 5, -12, 9, -21], key=abs)
[5, 9, -12, -21, 36]

key

reverse=True

>>> sorted([36, 5, -12, 9, -21], key=abs)
[36, -21, -12, 9, 5]

小结

返回函数

def lazy_sum(*args):
def sum():
ax = 0
for n in args:
ax = ax + n
return ax
return sum

f

>>> f()
25

lazy_sum

sum

小结

匿名函数

>>> list(map(lambda x: x * x, [1, 2, 3, 4, 5, 6, 7, 8, 9]))
[1, 4, 9, 16, 25, 36, 49, 64, 81]

lambda x: x * x

def f(x):
return x * x

lambda

x

小结

装饰器

>>> def now():
...     print('2015-3-25')
...
>>> f = now
>>> f()
2015-3-25

__name__

>>> now.__name__
'now'
>>> f.__name__
'now'

def log(func):
def wrapper(*args, **kw):
print('call %s():' % func.__name__)
return func(*args, **kw)
return wrapper

@log
def now():
print('2015-3-25')

now()

>>> now()
call now():
2015-3-25

@log

now()

now = log(now)

log()

now()

now

def log(text):
def decorator(func):
def wrapper(*args, **kw):
print('%s %s():' % (text, func.__name__))
return func(*args, **kw)
return wrapper
return decorator

@log('execute')
def now():
print('2015-3-25')

>>> now()
execute now():
2015-3-25

>>> now = log('execute')(now)

__name__

'now'

'wrapper'

>>> now.__name__
'wrapper'

functools.wraps

import functools

def log(func):
@functools.wraps(func)
def wrapper(*args, **kw):
print('call %s():' % func.__name__)
return func(*args, **kw)
return wrapper

import functools

def log(text):
def decorator(func):
@functools.wraps(func)
def wrapper(*args, **kw):
print('%s %s():' % (text, func.__name__))
return func(*args, **kw)
return wrapper
return decorator

小结

偏函数

functools.partial

*args

**kw

>>> import functools
>>> int2 = functools.partial(int, base=2)
>>> int2('1000000')
64
>>> int2('1010101')
85

小结

模块

abc.py

abc

abc.py

mycompany

mycompany.abc

__init__.py

__init__.py

使用模块

sys

hello

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

' a test module '

__author__ = 'Michael Liao'

import sys

def test():
args = sys.argv
if len(args)==1:
print('Hello, world!')
elif len(args)==2:
print('Hello, %s!' % args[1])
else:
print('Too many arguments!')

if __name__=='__main__':
test()

__author__

import sys

sys

sys

sys

sys

argv

argv

python3 hello.py

sys.argv

['hello.py']

python3 hello.py Michael

sys.argv

['hello.py', 'Michael]

if __name__=='__main__':
test()

hello

__name__

__main__

hello

if

if

hello.py

$ python3 hello.py
Hello, world!
$ python hello.py Michael
Hello, Michael!

$ python3
Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 23 2015, 02:52:03)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import hello
>>>

>>> hello.test()
Hello, world!

作用域

__xxx__

__author__

__name__

_xxx

__xxx

_abc

__abc

def _private_1(name):
return 'Hello, %s' % name

def _private_2(name):
return 'Hi, %s' % name

def greeting(name):
if len(name) > 3:
return _private_1(name)
else:
return _private_2(name)

greeting()

private

greeting()

private

安装第三方库

pip3

pip install Pillow

模块搜索路径

>>> import sys
>>> sys.path.append('/Users/michael/my_py_scripts')

面向对象编程

类和实例

class Student(object):
pass

>>> bart = Student()
>>> bart
<__main__.Student object at 0x10a67a590>
>>> Student
<class '__main__.Student'>

>>> bart.name = 'Bart Simpson'
>>> bart.name
'Bart Simpson'

__init__

name

score

class Student(object):

def __init__(self, name, score):
self.name = name
self.score = score

__init__

self

__init__

__init__

self

>>> bart = Student('Bart Simpson', 59)
>>> bart.name
'Bart Simpson'
>>> bart.score
59

数据封装

Student

name

score

Student

Student

class Student(object):

def __init__(self, name, score):
self.name = name
self.score = score

def print_score(self):
print('%s: %s' % (self.name, self.score))

self

小结

>>> bart = Student('Bart Simpson', 59)
>>> lisa = Student('Lisa Simpson', 87)
>>> bart.age = 8
>>> bart.age
8
>>> lisa.age
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'Student' object has no attribute 'age'

访问限制

__

class Student(object):

def __init__(self, name, score):
self.__name = name
self.__score = score

def print_score(self):
print('%s: %s' % (self.__name, self.__score))

实例变量.__name

实例变量.__score

>>> bart = Student('Bart Simpson', 98)
>>> bart.__name
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'Student' object has no attribute '__name'

Student

get_name

get_score

name

score

set_score

set_name

class Student(object):
...

def set_score(self, score):
if 0 <= score <= 100:
self.__score = score
else:
raise ValueError('bad score')

__xxx__

_name

__name

_Student__name

__name

>>> bart._Student__name
'Bart Simpson'

继承和多态

class Animal(object):
def run(self):
print('Animal is running...')

class Dog(Animal):

def run(self):
print('Dog is running...')

class Cat(Animal):

def run(self):
print('Cat is running...')

run()

Animal

run()

Animal

run_twice()

静态语言 vs 动态语言

Animal

run()

Animal

run()

小结

获取对象信息

使用type()

type()

>>> type(123)
<class 'int'>
>>> type('str')
<class 'str'>
>>> type(None)
<type(None) 'NoneType'>

>>> type(abs)
<class 'builtin_function_or_method'>
>>> type(a)
<class '__main__.Animal'>

>>> import types
>>> def fn():
...     pass
...
>>> type(fn)==types.FunctionType
True
>>> type(abs)==types.BuiltinFunctionType
True
>>> type(lambda x: x)==types.LambdaType
True
>>> type((x for x in range(10)))==types.GeneratorType
True

使用isinstance()

>>> h = Husky()
>>>> isinstance(h, Husky)
True

type()

isinstance()

>>> isinstance('a', str)
True
>>> isinstance(123, int)
True
>>> isinstance(b'a', bytes)
True

>>> isinstance([1, 2, 3], (list, tuple))
True
>>> isinstance((1, 2, 3), (list, tuple))
True

使用dir()

dir()

>>> dir('ABC')
['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'capitalize', 'casefold', 'center', 'count', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'format_map', 'index', 'isalnum', 'isalpha', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'maketrans', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

__xxx__

__len__

len()

len()

__len__()

lower()

getattr()

setattr()

hasattr()

>>> hasattr(obj, 'x') # 有属性'x'吗？
True
>>> obj.x
9
>>> hasattr(obj, 'y') # 有属性'y'吗？
False
>>> setattr(obj, 'y', 19) # 设置一个属性'y'
>>> hasattr(obj, 'y') # 有属性'y'吗？
True
>>> getattr(obj, 'y') # 获取属性'y'
19
>>> obj.y # 获取属性'y'
19

>>> hasattr(obj, 'power') # 有属性'power'吗？
True
>>> getattr(obj, 'power') # 获取属性'power'
<bound method MyObject.power of <__main__.MyObject object at 0x10077a6a0>>
>>> fn = getattr(obj, 'power') # 获取属性'power'并赋值到变量fn
>>> fn # fn指向obj.power
<bound method MyObject.power of <__main__.MyObject object at 0x10077a6a0>>
>>> fn() # 调用fn()与调用obj.power()是一样的
81

实例属性和类属性

class Student(object):
def __init__(self, name):
self.name = name

s = Student('Bob')
s.score = 90

Student

class Student(object):
name = 'Student'

>>> class Student(object):
...     name = 'Student'
...
>>> s = Student() # 创建实例s
>>> print(s.name) # 打印name属性，因为实例并没有name属性，所以会继续查找class的name属性
Student
>>> print(Student.name) # 打印类的name属性
Student
>>> s.name = 'Michael' # 给实例绑定name属性
>>> print(s.name) # 由于实例属性优先级比类属性高，因此，它会屏蔽掉类的name属性
Michael
>>> print(Student.name) # 但是类属性并未消失，用Student.name仍然可以访问
Student
>>> del s.name # 如果删除实例的name属性
>>> print(s.name) # 再次调用s.name，由于实例的name属性没有找到，类的name属性就显示出来了
Student

面向对象高级编程

使用

__slots__

class Student(object):
pass

>>> s = Student()
>>> s.name = 'Michael' # 动态给实例绑定一个属性
>>> print(s.name)
Michael

>>> def set_age(self, age): # 定义一个函数作为实例方法
...     self.age = age
...
>>> from types import MethodType
>>> s.set_age = MethodType(set_age, s) # 给实例绑定一个方法
>>> s.set_age(25) # 调用实例方法
>>> s.age # 测试结果
25

>>> def set_score(self, score):
...     self.score = score
...
>>> Student.set_score = set_score

使用

__slots__

__slots__

class Student(object):
__slots__ = ('name', 'age') # 用tuple定义允许绑定的属性名称

使用@property

s = Student()
s.score = 9999

set_score()

get_score()

class Student(object):

def get_score(self):
return self._score

def set_score(self, value):
if not isinstance(value, int):
raise ValueError('score must be an integer!')
if value < 0 or value > 100:
raise ValueError('score must between 0 ~ 100!')
self._score = value

@property

class Student(object):

@property
def score(self):
return self._score

@score.setter
def score(self, value):
if not isinstance(value, int):
raise ValueError('score must be an integer!')
if value < 0 or value > 100:
raise ValueError('score must between 0 ~ 100!')
self._score = value

@property

@property

@score.setter

>>> s = Student()
>>> s.score = 60 # OK，实际转化为s.set_score(60)
>>> s.score # OK，实际转化为s.get_score()
60
>>> s.score = 9999
Traceback (most recent call last):
...
ValueError: score must between 0 ~ 100!

class Student(object):

@property
def birth(self):
return self._birth

@birth.setter
def birth(self, value):
self._birth = value

@property
def age(self):
return 2015 - self._birth

birth

age

小结

@property

多重继承

class Dog(Mammal, Runnable):
pass

MixIn

class Dog(Mammal, RunnableMixIn, CarnivorousMixIn):
pass

小结

定制类

__xxx__

__str__()

>>> class Student(object):
...     def __init__(self, name):
...         self.name = name
...     def __str__(self):
...         return 'Student object (name: %s)' % self.name
...
>>> print(Student('Michael'))
Student object (name: Michael)

__repr__()

__str__()

__repr__()

class Student(object):
def __init__(self, name):
self.name = name
def __str__(self):
return 'Student object (name=%s)' % self.name
__repr__ = __str__

__iter__()

for ... in

__iter__()

__next__()

StopIteration

class Fib(object):
def __init__(self):
self.a, self.b = 0, 1 # 初始化两个计数器a，b

def __iter__(self):
return self # 实例本身就是迭代对象，故返回自己

def __next__(self):
self.a, self.b = self.b, self.a + self.b # 计算下一个值
if self.a > 100000: # 退出循环的条件
raise StopIteration();
return self.a # 返回下一个值

__getitem__

__getitem__()

class Fib(object):
def __getitem__(self, n):
a, b = 1, 1
for x in range(n):
a, b = b, a + b
return a

>>> f = Fib()
>>> f[0]
1
>>> f[1]
1
>>> f[2]
2

list

__getitem__()

__getattr__

__getattr__()

class Chain(object):

def __init__(self, path=''):
self._path = path

def __getattr__(self, path):
return Chain('%s/%s' % (self._path, path))

def __str__(self):
return self._path

__repr__ = __str__

>>> Chain().status.user.timeline.list
'/status/user/timeline/list'

__call__

instance.method()

__call__()

class Student(object):
def __init__(self, name):
self.name = name

def __call__(self):
print('My name is %s.' % self.name)

>>> s = Student('Michael')
>>> s() # self参数不要传入
My name is Michael.

Callable()

>>> callable(Student())
True
>>> callable(max)
True
>>> callable([1, 2, 3])
False
>>> callable(None)
False
>>> callable('str')
False

小结

使用枚举类

from enum import Enum

Month = Enum('Month', ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'))

Month

Month.Jan

>>> for name, member in Month.__members__.items():
...     print(name, '=>', member, ',', member.value)
...
Jan => Month.Jan , 1
Feb => Month.Feb , 2
Mar => Month.Mar , 3
Apr => Month.Apr , 4
May => Month.May , 5
Jun => Month.Jun , 6
Jul => Month.Jul , 7
Aug => Month.Aug , 8
Sep => Month.Sep , 9
Oct => Month.Oct , 10
Nov => Month.Nov , 11
Dec => Month.Dec , 12

value

int

1

Enum

from enum import Enum, unique

@unique
class Weekday(Enum):
Sun = 0 # Sun的value被设定为0
Mon = 1
Tue = 2
Wed = 3
Thu = 4
Fri = 5
Sat = 6

@unique

小结

Enum

使用元类

class Hello(object):
def hello(self, name='world'):
print('Hello, %s.' % name)

>>> def fn(self, name='world'): # 先定义函数
...     print('Hello, %s.' % name)
...
>>> Hello = type('Hello', (object,), dict(hello=fn)) # 创建Hello class
>>> h = Hello()
>>> h.hello()
Hello, world.

metaclass

错误、调试和测试

错误处理

open()

try

try:
print('try...')
r = 10 / int('2')
print('result:', r)
except ValueError as e:
print('ValueError:', e)
except ZeroDivisionError as e:
print('ZeroDivisionError:', e)
else:
print('no error!')
finally:
print('finally...')
print('END')

try

except

final

else

final

else

final

BaseException

try...except

调用堆栈

记录错误

# err_logging.py

import logging

def foo(s):
return 10 / int(s)

def bar(s):
return foo(s) * 2

def main():
try:
bar('0')
except Exception as e:
logging.exception(e)

main()
print('END')

抛出错误

raise

# err_reraise.py

def foo(s):
n = int(s)
if n==0:
raise ValueError('invalid value: %s' % s)
return 10 / n

def bar():
try:
foo('0')
except ValueError as e:
print('ValueError!')
raise

bar()

try:
10 / 0
except ZeroDivisionError:
raise ValueError('input error!')

小结

try...except...finally

调试

print()

print()

断言（assert）

def foo(s):
n = int(s)
assert n != 0, 'n is zero!'
return 10 / n

def main():
foo('0')

$ python3 err.py
Traceback (most recent call last):
...
AssertionError: n is zero!

$ python3 -O err.py
Traceback (most recent call last):
...
ZeroDivisionError: division by zero

logging

import logging

s = '0'
n = int(s)
logging.info('n = %d' % n)
print(10 / n)

logging.info()

debug

info

warning

error

debug

error

import logging
logging.basicConfig(level=logging.INFO)

pdg

python3 -m pdb err.py

l

n

p 变量名

q

pdb.set_trace()

# err.py
import pdb

s = '0'
n = int(s)
pdb.set_trace() # 运行到这里会自动暂停
print(10 / n)

p

c

IDE

单元测试

运行单元测试

if __name__ == '__main__':
unittest.main()

$ python3 -m unittest mydict_test

setUp与tearDown

小结

文档测试

小结

IO编程

文件读写

读文件

>>> f = open('/Users/michael/test.txt', 'r')

read()

>>> f.read()
'Hello, world!'

try ... finally

try:
f = open('/path/to/file', 'r')
print(f.read())
finally:
if f:
f.close()

with

close()

with open('/path/to/file', 'r') as f:
print(f.read())

read()

read(size)

readline()

readlines()

list

file-like Object

open()

read()

read()

StringIO

二进制文件

'rb'

>>> f = open('/Users/michael/test.jpg', 'rb')
>>> f.read()
b'\xff\xd8\xff\xe1\x00\x18Exif\x00\x00...' # 十六进制表示的字节

字符编码

open()

encoding

>>> f = open('/Users/michael/gbk.txt', 'r', encoding='gbk')
>>> f.read()
'测试'

写文件

>>> f = open('/Users/michael/test.txt', 'w')
>>> f.write('Hello, world!')
>>> f.close()

close()

with

with open('/Users/michael/test.txt', 'w') as f:
f.write('Hello, world!')

open()

encoding

小结

open()

with

StringIO和BytesIO

StringIO

>>> from io import StringIO
>>> f = StringIO()
>>> f.write('hello')
5
>>> f.write(' ')
1
>>> f.write('world!')
6
>>> print(f.getvalue())
hello world!

getvalue()

>>> from io import StringIO
>>> f = StringIO('Hello!\nHi!\nGoodbye!')
>>> while True:
...     s = f.readline()
...     if s == '':
...         break
...     print(s.strip())
...
Hello!
Hi!
Goodbye!

BytesIO

>>> from io import BytesIO
>>> f = BytesIO()
>>> f.write('中文'.encode('utf-8'))
6
>>> print(f.getvalue())
b'\xe4\xb8\xad\xe6\x96\x87'

>>> from io import StringIO
>>> f = BytesIO(b'\xe4\xb8\xad\xe6\x96\x87')
>>> f.read()
b'\xe4\xb8\xad\xe6\x96\x87'

小结

操作文件和目录

os

os.name

os.uname()

环境变量

os.environ

os.environ.get('key')

操作文件和目录

os

os.path

# 查看当前目录的绝对路径:
>>> os.path.abspath('.')
'/Users/michael'
# 在某个目录下创建一个新目录，首先把新目录的完整路径表示出来:
>>> os.path.join('/Users/michael', 'testdir')
'/Users/michael/testdir'
# 然后创建一个目录:
>>> os.mkdir('/Users/michael/testdir')
# 删掉一个目录:
>>> os.rmdir('/Users/michael/testdir')

os.path.split()

os.path.splitext()

# 对文件重命名:
>>> os.rename('test.txt', 'test.py')
# 删掉文件:
>>> os.remove('test.py')

shutil

copyfile()

shutil

os

小结

os

os

os.path

序列化

pickle

JSON

json

JSON进阶

class

小结

pickle

json

json

dumps()

loads()

进程和线程

小结

多进程

fork()

fork()

multiprocessing

fork

multiprocessing

multiprocessing

Process

from multiprocessing import Process
import os

# 子进程要执行的代码
def run_proc(name):
print('Run child process %s (%s)...' % (name, os.getpid()))

if __name__=='__main__':
print('Parent process %s.' % os.getpid())
p = Process(target=run_proc, args=('test',))
print('Child process will start.')
p.start()
p.join()
print('Child process end.')

Process

start()

join()

Pool

from multiprocessing import Pool
import os, time, random

def long_time_task(name):
print('Run task %s (%s)...' % (name, os.getpid()))
start = time.time()
time.sleep(random.random() * 3)
end = time.time()
print('Task %s runs %0.2f seconds.' % (name, (end - start)))

if __name__=='__main__':
print('Parent process %s.' % os.getpid())
p = Pool(4)
for i in range(5):
p.apply_async(long_time_task, args=(i,))
print('Waiting for all subprocesses done...')
p.close()
p.join()
print('All subprocesses done.')

Pool

join()

join()

close()

close()

Process

p = Pool(4)

Pool

子进程

subprocess

communicate()

进程间通信

Process

multiprocessing

Queue

Pipes

小结

fork()

multiprocessing

Queue

Pipes

多线程

_thread

threading

_thread

threading

_thread

threading

import time, threading

# 新线程执行的代码:
def loop():
print('thread %s is running...' % threading.current_thread().name)
n = 0
while n < 5:
n = n + 1
print('thread %s >>> %s' % (threading.current_thread().name, n))
time.sleep(1)
print('thread %s ended.' % threading.current_thread().name)

print('thread %s is running...' % threading.current_thread().name)
t = threading.Thread(target=loop, name='LoopThread')
t.start()
t.join()
print('thread %s ended.' % threading.current_thread().name)

Lock

多核CPU

小结

ThreadLocal

小结

ThreadLocal

ThreadLocal

进程 VS 线程

线程切换

计算密集型 vs. IO密集型

异步IO

分布式进程

multiprocessing

managers

小结

正则表达式

\d

\w

.

*

+

?

{n}

{n,m}

进阶

[]

[0-9a-zA-Z\_]

[0-9a-zA-Z\_]+

'a100'

'0_Z'

'Py3000'

[a-zA-Z\_][0-9a-zA-Z\_]*

[a-zA-Z\_][0-9a-zA-Z\_]{0, 19}

A|B

[P|p]ython

'Python'

'python'

^

^\d

$

\d$

py

'python'

^py$

'py'

re

模块

>>> import re
>>> re.match(r'^\d{3}\-\d{3,8}$', '010-12345')
<_sre.SRE_Match object; span=(0, 9), match='010-12345'>
>>> re.match(r'^\d{3}\-\d{3,8}$', '010 12345')
>>>

match()

Match

None

切分字符串

>>> re.split(r'\s+', 'a b   c')
['a', 'b', 'c']

分组

>>> m = re.match(r'^(\d{3})-(\d{3,8})$', '010-12345')
>>> m
<_sre.SRE_Match object; span=(0, 9), match='010-12345'>
>>> m.group(0)
'010-12345'
>>> m.group(1)
'010'
>>> m.group(2)
'12345'

贪婪匹配

?

编译

>>> import re
# 编译:
>>> re_telephone = re.compile(r'^(\d{3})-(\d{3,8})$')
# 使用：
>>> re_telephone.match('010-12345').groups()
('010', '12345')
>>> re_telephone.match('010-8086').groups()
('010', '8086')

小结

Python常用函数

int()

int(string)

float()

float(string)

str()

sum()

sum(itrable,start)

isinstance()