python 之金玉良言 或许是最后一次给自己系统总结--已结
jar tvf xxx.jar
vim xxx.jar （其实 底层调用 unzip , zip 命令)
配置一下 notepad++ F5
cmd /k D:"Program Files (x86)"\python\python.exe "$(FULL_CURRENT_PATH)" &pause &exit
# 查看已经连接过的 wifi 密码
for /f "skip=9 tokens=1,2 delims=:" %i in ('netsh wlan show profiles') do @echo %j | findstr -i -v echo | netsh wlan show profiles %j key=clear
进入 venv 生成 requirements.txt
pip freeze > requirements.txt
pip install -r requirements.txt
关键字： DAG 有向无环图 ， 最左原则 实现 MRO (method resolution order) 方法解析顺序 之继承链
java 说我还是不太相信你，还是给你定一个规范吧， python 说 你是个成年人了，你知道为你的代码负责
不要对实例属性和类属性使用相同的名字，否则将产生难以发现的错误。实力属性总是会覆盖 类属型
getattr()、setattr()以及hasattr() ,dir() 内省
map filter 为 iter惰性计算的 Iterator, reduce 跟sorted 却是 立即计算
模块搜索路径
当我们试图加载一个模块时，Python会在指定的路径下搜索对应的.py文件，如果找不到，就会报错：
try:#python2
from UserDict import UserDict
#建议按照python3的名字进行import
from UserDict import DictMixin as MutableMapping
except ImportError:#python3
from collections import UserDict
from collections import MutableMapping
>>> import mymodule
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named mymodule
默认情况下，Python解释器会搜索当前目录、所有已安装的内置模块和第三方模块，搜索路径存放在sys模块的path变量中：
>>> import sys
>>> sys.path
['', '/Library/Frameworks/Python.framework/Versions/3.6/lib/python36.zip', '/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6', ..., '/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages']
如果我们要添加自己的搜索目录，有两种方法：
一是直接修改sys.path，添加要搜索的目录：
>>> import sys
>>> sys.path.append('/Users/michael/my_py_scripts')
这种方法是在运行时修改，运行结束后失效。
第二种方法是设置环境变量PYTHONPATH，该环境变量的内容会被自动添加到模块搜索路径中。设置方式与设置Path环境变量类似。注意只需要添加你自己的搜索路径，Python自己本身的搜索路径不受影响。
set和dict的唯一区别仅在于没有存储对应的value，但是，set的原理和dict一样，所以，同样不可以放入可变对象，因为无法判断两个可变对象是否相等，也就无法保证set内部“不会有重复元素”。
请务必注意，dict内部存放的顺序和key放入的顺序是没有关系的。
和list比较，dict有以下几个特点：
查找和插入的速度极快，不会随着key的增加而变慢；
需要占用大量的内存，内存浪费多。
而list相反：
查找和插入的时间随着元素的增加而增加；
占用空间小，浪费内存很少。
所以，dict是用空间来换取时间的一种方法。
dict可以用在需要高速查找的很多地方，在Python代码中几乎无处不在，正确使用dict非常重要，需要牢记的第一条就是dict的key必须是不可变对象。
这是因为dict根据key来计算value的存储位置，如果每次计算相同的key得出的结果不同，那dict内部就完全混乱了。这个通过key计算位置的算法称为哈希算法（Hash）。
要保证hash的正确性，作为key的对象就不能变。在Python中，字符串、整数等都是不可变的，因此，可以放心地作为key。而list是可变的，就不能作为key：
>>> key = [1, 2, 3]
>>> d[key] = 'a list'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
l = [4,5,6]
t = (1,)
s = {1}
# s = set([1,2,3])
d = {'name':'frank'}
help(abs)
把函数作为参数传入，这样的函数称为高阶函数，函数式编程就是指这种高度抽象的编程范式。
from functools import reduce
import re
exp = '99 + 88 + 7.6 ='
reduce(lambda x,y:float(x)+float(y),
filter(lambda x:True if x else False,
map(lambda x:x.strip(),
re.split(r'[\+=]',exp))))
为什么要设计str、None这样的不变对象呢？因为不变对象一旦创建，对象内部的数据就不能修改，这样就减少了由于修改数据导致的错误。此外，由于对象不变，多任务环境下同时读取对象不需要加锁，同时读一点问题都没有。我们在编写程序时，如果可以设计一个不变对象，那就尽量设计成不变对象。
凡是可作用于for循环的对象都是Iterable类型；
凡是可作用于next()函数的对象都是Iterator类型，它们表示一个惰性计算的序列；
集合数据类型如list、dict、str等是Iterable但不是Iterator，不过可以通过iter()函数获得一个Iterator对象。
Python的for循环本质上就是通过不断调用next()函数实现的，例如：
for x in [1, 2, 3, 4, 5]:
pass
实际上完全等价于：
# 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
"""
练习
小明身高1.75，体重80.5kg。请根据BMI公式（体重除以身高的平方）帮小明计算他的BMI指数，并根据BMI指数：
低于18.5：过轻
18.5-25：正常
25-28：过重
28-32：肥胖
高于32：严重肥胖
"""
height = 1.75
weight = 80.5
def BMI(height,weight):
bmi = (weight/height)**2
results = ("过轻","正常","过重","肥胖","严重肥胖")
ret = results[-1]
if bmi<18.5:
ret = results[0]
elif 18.5<=bmi<25:
ret = results[1]
elif 25<=bmi<28:
ret = results[2]
elif 28<=bmi<32:
ret = results[3]
else:
pass
return ret
BMI(height,weight)
def myhex(num):
hex_list = []
t_mt = ('A','B','C','D','E','F')
while True:
mod_, num = num %16, num//16
hex_list.append(t_mt[mod_-10]) if mod_>9 else hex_list.append(str(mod_))
if num== 0 :
break
hex_list.append('0x')
hex_list.reverse()
return ''.join(hex_list)
myhex(25)
def my_octonary(num):
octonary_list = []
while True:
mod_,num = num%8,num//8
octonary_list.append(str(mod_))
if num == 0:
break
octonary_list.append('0o')
octonary_list.reverse()
return ''.join(octonary_list)
my_octonary(9)
# 基本递归
def fac(n):
if n>1:
return n*fac(n-1)
elif n==1:
return 1
else:
raise ValueError('数值必须大于等于1')
# 尾递归方式
def fac_iter(num,product):
if num==1:
return product
else:
return fac_iter(num-1,num*product)
# 循环实现
def fac2(n):
if n<1:
raise ValueError('数值必须大于等于1')
acc = 1
while n>=1:
acc*=n
n-=1
return acc
fac_iter(4,1)
str2float
# -*- coding: utf-8 -*-
from functools import reduce
digital_dict = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}
def str2float(s):
i,j = s.split('.')
left = reduce(lambda x,y:x*10+y,map(lambda x:digital_dict.get(x),i))
right = reduce(lambda x,y:x/10+y,list(map(lambda x:digital_dict.get(x),j))[::-1])/10
return left+right
str2float('123.456')
累乘
# -*- coding: utf-8 -*-
from functools import reduce
def prod(L):
return reduce(lambda x,y:x*y,L)
print('3 * 5 * 7 * 9 =', prod([3, 5, 7, 9]))
if prod([3, 5, 7, 9]) == 945:
print('测试成功!')
else:
print('测试失败!')
名字这个我改了测试
names = ['adam', 'LISA', 'barT']
def normalize(names):
return list(map(lambda name:str.upper(name[0])+str.lower(name[1:]),names))
# normalize(names)
# 测试:
L1 = ['adam', 'LISA', 'barT']
L2 = normalize(L1)
print(L2)
str2int
digital_dict = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}
from functools import reduce
def str2int(s):
return reduce(lambda x,y:x*10+y,map(lambda x:digital_dict.get(x),s))
str2int('13579')
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
def _odd_iter3():
n = 3
while True:
yield n
n+=2
def _not_divisible_3(n):
return lambda x:x%n>0
def prime_iter3():
yield 2
it = _odd_iter()
while True:
base_num = next(it)
yield base_num
it = filter(lambda x,y=base_num:x%y>0,it)
for i in prime_iter3():
if i>50:
break
else:
print(i,end=',')
# -*- coding: utf-8 -*-
L = [('Bob', 75), ('Adam', 92), ('Bart', 66), ('Lisa', 88)]
def by_score(x):
return x[1]
def by_name(x):
return x[0]
sorted(L,key=by_score,reverse=True)
sorted(L,key=by_name,reverse=True)
def createCounter():
count = 0
def counter():
nonlocal count
count += 1
return count
return counter
def createCounter():
def f():
n=1
while True:
yield n
n +=1
g=f()
def counter():
return next(g)
return counter
# 测试:
counterA = createCounter()
print(counterA(), counterA(), counterA(), counterA(), counterA()) # 1 2 3 4 5
counterB = createCounter()
if [counterB(), counterB(), counterB(), counterB()] == [1, 2, 3, 4]:
print('测试通过!')
else:
print('测试失败!')
def createCounter():
x = 0
def counter():
nonlocal x
x += 1
return x
return counter
from collections import Counter
Counter(s=3, c=2, e=1, u=1)
Counter({'s': 3, 'c': 2, 'u': 1, 'e': 1})
some_data=('c', '2', 2, 3, 5, 'c', 'd', 4, 5, 'd', 'd')
Counter(some_data).most_common(2)
[('d', 3), ('c', 2)]
some_data=['c', '2', 2, 3, 5, 'c', 'd', 4, 5, 'd', 'd']
Counter(some_data).most_common(2)
[('d', 3), ('c', 2)]
some_data={'c', '2', 2, 3, 5, 'c', 'd', 4, 5, 'd', 'd'}
Counter(some_data).most_common(2)
[('c', 1), (3, 1)]
class Fib():
# 构造方法
def __init__(self,a=0,b=1):
self.__a,self.__b = a,b
def __enter__(self):
print('Begin')
# 这里 实际可以新增 打开资源动作
return self
def __exit__(self,exc_type,exc_value,traceback):
if exc_type:
print('Error')
else:
print('End')
#生成器 1
def __iter__(self):
return self
# 生成器 2
def __next__(self):
self.__a, self.__b = self.__b, self.__a + self.__b
if self.__a >10:
raise StopIteration()
return self.__a
def __generatorfib(self,start,stop):
x, y = 1,1
print(start,'-->',stop)
begin = int(start)
end = int(stop)
while begin<=end:
yield x
x, y = y,x+y
begin, end = begin+1,end-1
# 做成可下标取
def __getitem__(self,n):
if isinstance(n,int):
x, y = 1,1
for i in range(n):
x, y = y,x+y
return x
# 下面这个没有真正支持 step
if isinstance(n,slice):
start = n.start if n.start else 0
stop = n.stop
step = n.step
x,y = 1,1
L = []
for n in range(0,stop,step):
if n>=start:
L.append(x)
x, y = y,x+y
return L[start:stop:step]
# if isinstance(n,slice):
# start = slice.start
# stop = slice.stop
# step = slice.step
# inner_fib = self.__generatorfib(start,stop)
# L = list(inner_fib)
# return L[start,stop,step]
def __getattr__(self,attr):
if attr=='age':
return lambda :18
raise AttributeError('\'Fib\' object has no attribute \'{}\''.format(attr))
# 打印给 user 看
def __str__(self):
return 'Fib({},{})'.format(self.__a,self.__b)
# 打印给程序员看
def __repr__(self):
return self.__str__()
# 重复声明一次是多余的但是指出这种用法
__repr__ = __str__
for n in eval('Fib(0,1)'):
print(n,end=',')
with Fib() as f:
f[0:5:1]
f.age()
f.score()
元类 暂时学到这儿 ，产生 class 对象的 模板 必须继承自 type , 先有类来后有天，元类更在类之前, python 的 动态特性简直如此憨直 动到极致
class Field(object):
def __init__(self,name,column_type):
self.name = name
self.column_type = column_type
def __str__(self):
return 'Field({name},{column_type})'.format(name=self.name,column_type=self.column_type)
__repr__ = __str__
class IntegerField(Field):
def __init__(self,name):
super(IntegerField,self).__init__(name,'bigint')
class VarcharField(Field):
def __init__(self,name):
super(VarcharField,self).__init__(name,'varchar(256)')
class ModelMetaclass_frank(type):
def __new__(cls,name,bases,attrs):
if name=='Model':
return type.__new__(cls,name,bases,attrs)
print('found sub-model: {sub_model}'.format(sub_model=name))
#准备一个 object 属性 与 列关系映射
mappings = {}
# 遍历 类属性仅 将 instance 为 Field 的 添加到 mappings 里保存起来
for attr_key,attr_value in attrs.items():
# attr_value ==》
if isinstance(attr_value,Field):
print('Found mapping: {}==>{}'.format(attr_key,attr_value))
mappings[attr_key] = attr_value
# 去除掉 attr (类属性) 中 有的，但是 mappings(可以看作是 实例属性 这里有点绕 这里的 实例是 type 创建出来的 class 实例) 中也有的 属性 ，避免 属性覆盖
for instance_key in mappings.keys():
attrs.pop(instance_key)
# 将保存好的 实例属性 以及 table 名字 保留到 attr 中
attrs['__mappings__'] = mappings
attrs['__table__'] = str.lower(name) # 这里的 那么 完全可以改为 xxx_+ name 比如 订单 register_user ,login_user
return type.__new__(cls,name,bases,attrs)
class Model(dict,metaclass=ModelMetaclass_frank):
def __init__(self,*args,**kw):
super(Model, self).__init__(*args,**kw)
def __getattr__(self,key):
try:
value = self.get(key)
except KeyError as e:
raise AttributeError(r'"Model" object has no attribute "{}"'.format(key))
return value
# def __setattr__(self,key,value):
# self[key] = value
def save(self):
fields = []
params = []
args = []
for instance_attr_key,instance_attr_value in self.__mappings__.items():
fields.append(instance_attr_value.name) # 这里是 Field 类中的 self.name
params.append('?')
# print('-->',getattr(self,instance_attr_key,None))
# args.append(getattr(self,instance_attr_key,None))
args.append(self.__getattr__(instance_attr_key))
print('fiels: --> ',','.join(fields))
print('params: -->',','.join(params))
print('args: -->',args)
args = list(map(lambda s: '\''+s+'\'' if isinstance(s,str) else str(s),args))
sql = 'insert into {table_name}({fields_str}) values({values})'.format(table_name=self.__table__,fields_str=','.join(fields),values=','.join(args))
print(sql)
class User(Model):
# 定义类的属性到列的映射：
id = IntegerField('id')
name = VarcharField('username')
email = VarcharField('email')
password = VarcharField('password')
# 创建一个实例：
u = User(id=12345, name='Michael', email='test@orm.org', password='my-pwd')
u.save()
class Field(object):
def __init__(self,name,column_type):
self.name = name
self.column_type = column_type
def __str__(self):
return ''.format(name=self.name,column_type=self.column_type)
class IntegerField(Field):
def __init__(self,name):
super(IntegerField,self).__init__(name,'bigint')
class StringField(Field):
def __init__(self,name):
return super(StringField,self).__init__(name,'varchar(256)')
# 元类必须继承自 type
class ModelMetaclass(type):
def __init__(self,*args,**kw):
return super(ModelMetaclass,self).__init__(*args,**kw)
def __new__(cls,name,bases,attrs):
print(cls,'<-->',name)
if name=='Model':
return type.__new__(cls,name,bases,attrs)
print('Founding sub-model {sub_model}'.format(sub_model=name))
mappings = {}
for k,v in attrs.items():
if isinstance(v,Field):
mappings[k] = v
for k in mappings.keys():
attrs.pop(k)
attrs['__mappings__'] = mappings
attrs['__table__'] = attrs.get('__table__',str.lower(name))
return type.__new__(cls,name,bases,attrs)
class Model(dict,metaclass=ModelMetaclass):
def __init__(self,*args,**kw):
super(Model,self).__init__(*args,**kw)
def __getattr__(self,key):
try:
value = self.get(key)
except KeyError:
raise('\'{object}\' has no attr \'{attr}\''.format(object=self.__name__,attr=key))
return value
def save(self):
fields = []
args = []
for k,v in self.__mappings__.items():
fields.append(v.name)
args.append(self.__getattr__(k))
field_list = ','.join(fields)
arg_list = ','.join(list(map(lambda x: '\'{}\''.format(x) if isinstance(x,str) else str(x),args)))
sql = 'insert into {table_name}({field_list}) values({arg_list})'.format(table_name=self.__table__,field_list=field_list,arg_list=arg_list)
print(sql)
class LoginUser(Model):
id = IntegerField('id')
name = StringField('name')
email = StringField('email')
password = StringField('password')
__table__ = 'loginuser'
class RegisterUser(Model):
id = IntegerField('id')
name = StringField('name')
email = StringField('email')
password = StringField('password')
__table__ = 'registeruser'
login_user = LoginUser(id=1,name='Frank',email='frank@whatever.com',password='passwordxxx')
login_user.save()
register_user = RegisterUser(id=1,name='Frank',email='frank@whatever.com',password='passwordxxx')
register_user.save()
内建模块
# datetime
from datetime import datetime,timedelta
now = datetime.now()
# datetime 转 timestamp
now_timestamp = now.timestamp()
# timestampe 转本地 datetime
dt_local = datetime.fromtimestamp(now_timestamp)
# timestampe 转utc datetime
dt_utc = datetime.utcfromtimestamp(now_timestamp)
# 时间戳 没有时区， datetime中携带
print(dt_local.timestamp(),'<-->',dt_utc.timestamp())
print('{}\n{}\n{}\n{}'.format(now,now_timestamp,dt_local,dt_utc))
# 获取指定 日期和时间
year = 2019
month =3
day =3
hour = 15
minute = 7
dt_specified = datetime(year,month,day,hour,minute)
print(dt_specified)
# str 转 datetime str parse
datetime_str = '2019-03-03 15:22:00'
datetime_parse_format = '%Y-%m-%d %H:%M:%S'
cday = datetime.strptime(datetime_str,datetime_parse_format)
print(cday)
# datetime 转 str str format
print(cday.strftime('%Y/%m/%d'))
# 日期变化（delta） 用 timedelta
now = datetime.now()
now_next3_hours = now+timedelta(hours=3)
now_previous3_days = now+timedelta(days=-3)
print('next 3 hours: {}'.format(now_next3_hours))
print('now_previous3_days: {}'.format(now_previous3_days))
from datetime import timezone
tz_utc_8 = timezone(timedelta(hours=8))
now = datetime.now()
# 一开始 now 时区信息为 None
print(now.tzinfo)
# 暴力设置一个时区
now.replace(tzinfo=tz_utc_8)
print(now)
utc_now = datetime.utcnow()
# 一开始这玩意儿压根木有时区信息啊
print(utc_now.tzinfo)
# 暴力设置时区信息
utc_now = utc_now.replace(tzinfo=timezone.utc)
#北京日期时间 东八区
bj_dt = utc_now.astimezone(timezone(timedelta(hours=8)))
# 西八区
pst_dt = utc_now.astimezone(timezone(timedelta(hours=-8)))
# 东 9 区
tokyo_dt = utc_now.astimezone(timezone(timedelta(hours=9)))
print('bj_dt: ',bj_dt)
print('pst_dt: ',pst_dt)
print('tokyo_dt: ',tokyo_dt)
from datetime import datetime, timezone,timedelta
import re
def to_timestamp(dt_str,tz_str):
re_dt_str_1 = r'\d{4}-\d{1,2}-\d{1,2}\s\d{1,2}:\d{1,2}:\d{1,2}'
re_tz_str = r'^UTC([+-])(\d{1,2}):\d{2}$'
tz_grps = re.match(re_tz_str,tz_str).groups()
sign = tz_grps[0]
hours = int(tz_grps[1])
if re.match(re_dt_str_1,dt_str):
dt = datetime.strptime(dt_str,'%Y-%m-%d %H:%M:%S')
if sign=='+':
tz_info_x = timezone(timedelta(hours=hours))
else:
tz_info_x = timezone(timedelta(hours=-hours))
dt = dt.replace(tzinfo=tz_info_x)
else:
print('re is wrong!')
return dt.timestamp()
# 测试:
t1 = to_timestamp('2015-6-1 08:10:30', 'UTC+7:00')
assert t1 == 1433121030.0, t1
t2 = to_timestamp('2015-5-31 16:10:30', 'UTC-09:00')
assert t2 == 1433121030.0, t2
print('ok')
collections 模块
def chunks(l, n):
return [l[i:i+n] for i in range(0, len(l), n)]
chunks(s,2)
from collections import Iterator, Iterable
from collections import defaultdict
from collections import Counter, ChainMap, OrderedDict, namedtuple, deque
from itertools import islice # 替代 切片，但是只能 是正数
from itertools import zip_longest # 替代 zip 可以 对不一样个数的 进行迭代
from concurrent.futures import ThreadPoolExecutor as Pool
from collections import namedtuple, deque, defaultdict, OrderedDict, ChainMap, Counter
Point = namedtuple('Poing',['x','y','z'])
p = Point(1,2,3)
print(p.x,'--',p.y,'--',p.z)
# 双向列表
dq = deque([1,2,3,4])
dq.append(5)
dq.appendleft('a')
dq.popleft()
default_dict = defaultdict(lambda:'N/A') # 多了一个默认值
default_dict['name']='frank'
default_dict['age']
od = OrderedDict([('b',1),('a',2),('c',3)]) # 按照插入的顺序有序
od.get('a')
# 可以实现一个FIFO（先进先出）的dict，当容量超出限制时，先删除最早添加的Key
from collections import OrderedDict
class LastUpdatedOrderedDict(OrderedDict):
def __init__(self, capacity):
super(LastUpdatedOrderedDict, self).__init__()
self._capacity = capacity
def __setitem__(self, key, value):
containsKey = 1 if key in self else 0
if len(self) - containsKey >= self._capacity:
last = self.popitem(last=False)
print('remove:', last)
if containsKey:
del self[key]
print('set:', (key, value))
else:
print('add:', (key, value))
OrderedDict.__setitem__(self, key, value)
# 应用场景 设置参数优先级
from collections import ChainMap
import os, argparse
# 构造缺省参数:
defaults = {
'color': 'red',
'user': 'guest'
}
# 构造命令行参数:
parser = argparse.ArgumentParser()
parser.add_argument('-u', '--user')
parser.add_argument('-c', '--color')
namespace = parser.parse_args()
command_line_args = { k: v for k, v in vars(namespace).items() if v }
# 组合成ChainMap:
combined = ChainMap(command_line_args, os.environ, defaults)
# 打印参数:
print('color=%s' % combined['color'])
print('user=%s' % combined['user'])
c = Counter()
for ch in 'programing':
c[ch] +=1
print(c)
c = dict()
for ch in 'programing':
if ch in c:
c[ch] +=1
else:
c[ch] = 1
给单词按首字母分组
方法一:
words = ['apple','bat','bar','atom','book']
by_letter_grp_dict = {}
for word in words:
letter = word[0]
if letter in by_letter_grp_dict:
by_letter_grp_dict[letter].append(word)
else:
by_letter_grp_dict[letter] = [word]
print(by_letter_grp_dict)
方法二:
内置的collections模块有一个叫做defaultdict的类，它可以使该过程更简单。传入一个类型或函数（用于生成字典各插槽所使用的默认值）即可创建一个defaultdict：
words = ['apple','bat','bar','atom','book']
from collections import defaultdict
by_letter = defaultdict(list)
for word in words:
by_letter[word[0]].append(word)
print by_letter
#defaultdict(<type 'list'>, {'a': ['apple', 'atom'], 'b': ['bat', 'bar', 'book']})
计数使用collections 库的 Counter
>>> from collections import Counter
>>> c = Counter('hello world!')
>>> c
Counter({'l': 3, 'o': 2, 'h': 1, 'e': 1, ' ': 1, 'w': 1, 'r': 1, 'd': 1, '!': 1})
>>> c.most_common(1)
[('l', 3)]
>>> c.most_common(3)
[('l', 3), ('o', 2), ('h', 1)]
>>>
>>> import collections
>>> Card = collections.namedtuple('Card',['rank','suit'])
>>> class French_Deck(object):
... rank = [ str(i) for i in range(2,11,1)] + list('JQKA')
... suit = 'Spade,Club,Heart,Diamond'.split(',')
... def __init__(self):
... self._cards = [Card(r,s) for s in suit for r in rank]
... def __getitem__(self,position):
... return self._cards[position]
... def __len__(self):
... return len(self._cards)
...
>>> cards = French_Deck()
>>> len(cards)
56
from collections import namedtuple
stock_list = [['AAPL','10.30','11.90'],['YAHO','9.23','8.19'],['SINA','22.80','25.80']]
stock_info = namedtuple('stock_info',['name','start','end'])
[stock_info(name,start,end) for name,start,end in stock_list ]
stock_list
# 与 update 不一样哦。。。
from collections import ChainMap
dict_1 = {'name':'Frank','age':18}
dict_2 = {'name':'','age':20}
dict_coalesce = ChainMap(dict_1,dict_2)
dict_coalesce['name']
itertools 模块
from itertools import count, cycle, repeat, takewhile , chain, groupby
for i in count(1):
if i<=10:
print(i,end=',')
else:
break
print('\n'+'*'*100+'\n')
nums = takewhile(lambda n:n<=10,count(1))
print(list(nums))
for nl in repeat('\n',3):
print(nl)
c = 0
for ch in cycle('ABC'):
if c>=10:
break
else:
print(ch,end=',')
c+=1
print('\n'+'*'*100+'\n')
for ch in chain('ABC','XYZ'):
print(ch)
for key,group in groupby('AAAaaabbBBBBBBBCCCccccddddEEEEDDD',lambda ch:ch.upper()):
print(key,'--> ',list(group))
# -*- coding: utf-8 -*-
import itertools
from functools import reduce
def pi(N):
' 计算pi的值 '
# step 1: 创建一个奇数序列: 1, 3, 5, 7, 9, ...
odd_iter = itertools.count(1,2)
# step 2: 取该序列的前N项: 1, 3, 5, 7, 9, ..., 2*N-1.
odd_head = itertools.takewhile(lambda n:n<=2*N-1,odd_iter)
# print(list(odd_head),end=',')
# step 3: 添加正负符号并用4除: 4/1, -4/3, 4/5, -4/7, 4/9, ...
odd_final = [4/n * ((-1)**i) for i,n in enumerate(odd_head)]
# step 4: 求和:
value = reduce(lambda x,y:x+y,odd_final)
return value
# 测试:
print(pi(10))
print(pi(100))
print(pi(1000))
print(pi(10000))
assert 3.04 < pi(10) < 3.05
assert 3.13 < pi(100) < 3.14
assert 3.140 < pi(1000) < 3.141
assert 3.1414 < pi(10000) < 3.1415
print('ok')
contextlib 模块
from contextlib import contextmanager,closing
xml.parsers.expat , lxml 等 模块
import lxml
from xml.parsers.expat import ParserCreate
class DefaultSaxHandler(object):
def start_element(self, name, attrs):
print('sax:start_element: %s, attrs: %s' % (name, str(attrs)))
def end_element(self, name):
print('sax:end_element: %s' % name)
def char_data(self, text):
print('sax:char_data: %s' % text)
xml = r'''<?xml version="1.0"?>
<ol>
<li><a href="/python">Python</a></li>
<li><a href="/ruby">Ruby</a></li>
</ol>
'''
handler = DefaultSaxHandler()
parser = ParserCreate()
parser.StartElementHandler = handler.start_element
parser.EndElementHandler = handler.end_element
parser.CharacterDataHandler = handler.char_data
parser.Parse(xml)
html 解析模块 html
from html.parser import HTMLParser
from html.entities import name2codepoint
class MyHTMLParser(HTMLParser):
def handle_starttag(self, tag, attrs):
print('<%s>' % tag)
def handle_endtag(self, tag):
print('</%s>' % tag)
def handle_startendtag(self, tag, attrs):
print('<%s/>' % tag)
def handle_data(self, data):
print(data)
def handle_comment(self, data):
print('<!--', data, '-->')
def handle_entityref(self, name):
print('&%s;' % name)
def handle_charref(self, name):
print('&#%s;' % name)
parser = MyHTMLParser()
parser.feed('''<html>
<head></head>
<body>
<!-- test html parser -->
<p>Some <a href=\"#\">html</a> HTML tutorial...<br>END</p>
</body></html>''')
第三方 字符编码检测模块 chardet
import chardet
data = '最新の主要ニュース'.encode('euc-jp')
chardet.detect(data)
{'confidence': 0.99, 'encoding': 'EUC-JP', 'language': 'Japanese'}
其他第三方模块
青出于蓝的 requests >> urllib
Pillow(新) PIL(2.7 远古时代)
psutils <== process and system utilities
将字典的值转成object 的属性，递归
d = {'a': 1, 'b': {'c': 2}, 'd': ["hi", {'foo': "bar"}]}
def my_dict2obj(args):
class obj(object):
def __init__(self,d):
for key,value in d.items():
if not isinstance(value,(list,tuple)):
setattr(self,key,obj(value) if isinstance(value,dict) else value)
else:
setattr(self,key,[obj(i) if isinstance(i,dict) else i for i in value])
return obj(args)
x = my_dict2obj(d)
print(x.d)
扩展拆箱
>>> a = [1,2,3,4,5,6]
>>> b,*c,d,e = a
>>> b
1
>>> c
[2, 3, 4]
>>> d
5
>>> e
6
给单词按首字母分组
方法一:
words = ['apple','bat','bar','atom','book']
by_letter_grp_dict = {}
for word in words:
letter = word[0]
if letter in by_letter_grp_dict:
by_letter_grp_dict[letter].append(word)
else:
by_letter_grp_dict[letter] = [word]
print(by_letter_grp_dict)
方法二:
内置的collections模块有一个叫做defaultdict的类，它可以使该过程更简单。传入一个类型或函数（用于生成字典各插槽所使用的默认值）即可创建一个defaultdict：
words = ['apple','bat','bar','atom','book']
from collections import defaultdict
by_letter = defaultdict(list)
for word in words:
by_letter[word[0]].append(word)
print by_letter
#defaultdict(<type 'list'>, {'a': ['apple', 'atom'], 'b': ['bat', 'bar', 'book']})
计数使用collections 库的 Counter
>>> from collections import Counter
>>> c = Counter('hello world!')
>>> c
Counter({'l': 3, 'o': 2, 'h': 1, 'e': 1, ' ': 1, 'w': 1, 'r': 1, 'd': 1, '!': 1})
>>> c.most_common(1)
[('l', 3)]
>>> c.most_common(3)
[('l', 3), ('o', 2), ('h', 1)]
>>>
我见青山多巍峨,料青山见我应如是
# -*- coding: utf-8 -*-
__author__ = 'Frank Li'
import socket
server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server.bind(('127.0.0.1',6666))
clients = set()
print('server bind 127.0.0.1:6666...')
while 1:
try:
data,addr = server.recvfrom(1024)
clients.add(addr)
if not data or data.decode('utf-8')=='pong':
continue
print('%s:%s >>> %s' % (addr[0],addr[1],data.decode('utf-8')))
for usr in clients:
if usr!=addr:
server.sendto(('%s:%s >>> %s' % (addr[0],addr[1],data.decode('utf-8'))).encode('utf-8'),usr)
except Exception as e:
pass
# -*- coding: utf-8 -*-
__author__ = 'Frank Li'
import socket,threading,os
client = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
client.sendto(b'pong',('127.0.0.1',6666))
def myinput():
while 1:
try:
msg = input('>>>')
yield msg
except Exception as e:
os._exit(0)
def getMsg(client):
while 1:
try:
r = client.recv(1024)
print('\n',r.decode('utf-8'),'\n>>>',end='')
except Exception as e:
pass
c = myinput()
def sendMsg(msg):
while 1:
msg = next(c)
client.sendto(msg.encode('utf-8'),('127.0.0.1',6666))
threading.Thread(target=sendMsg,args=(client,)).start()
threading.Thread(target=getMsg,args=(client,)).start()
inspect
import inspect
def a(a, b=0, *c, d, e=1, **f):
pass
aa = inspect.signature(a)
print("inspect.signature(fn)是:%s" % aa)
print("inspect.signature(fn)的类型：%s" % (type(aa)))
print("\n")
bb = aa.parameters
print("signature.paramerters属性是:%s" % bb)
print("ignature.paramerters属性的类型是%s" % type(bb))
print("\n")
for cc, dd in bb.items():
print("mappingproxy.items()返回的两个值分别是：%s和%s" % (cc, dd))
print("mappingproxy.items()返回的两个值的类型分别是：%s和%s" % (type(cc), type(dd)))
print("\n")
ee = dd.kind
print("Parameter.kind属性是:%s" % ee)
print("Parameter.kind属性的类型是:%s" % type(ee))
print("\n")
gg = dd.default
print("Parameter.default的值是: %s" % gg)
print("Parameter.default的属性是: %s" % type(gg))
print("\n")
ff = inspect.Parameter.KEYWORD_ONLY
print("inspect.Parameter.KEYWORD_ONLY的值是:%s" % ff)
print("inspect.Parameter.KEYWORD_ONLY的类型是:%s" % type(ff))
import inspect
def func_a(arg_a, *args, arg_b='hello', **kwargs):
print(arg_a, arg_b, args, kwargs)
if __name__ == '__main__':
# 获取函数签名
func_signature = inspect.signature(func_a)
func_args = []
# 获取函数所有参数
for k, v in func_signature.parameters.items():
# 获取函数参数后，需要判断参数类型
# 当kind为 POSITIONAL_OR_KEYWORD，说明在这个参数之前没有任何类似*args的参数，那这个函数可以通过参数位置或者参数关键字进行调用
# 这两种参数要另外做判断
if str(v.kind) in ('POSITIONAL_OR_KEYWORD', 'KEYWORD_ONLY'):
# 通过v.default可以获取到参数的默认值
# 如果参数没有默认值，则default的值为：class inspect_empty
# 所以通过v.default的__name__ 来判断是不是_empty 如果是_empty代表没有默认值
# 同时，因为类本身是type类的实例，所以使用isinstance判断是不是type类的实例
if isinstance(v.default, type) and v.default.__name__ == '_empty':
func_args.append({k: None})
else:
func_args.append({k: v.default})
# 当kind为 VAR_POSITIONAL时，说明参数是类似*args
elif str(v.kind) == 'VAR_POSITIONAL':
args_list = []
func_args.append(args_list)
# 当kind为 VAR_KEYWORD时，说明参数是类似**kwargs
elif str(v.kind) == 'VAR_KEYWORD':
args_dict = {}
func_args.append(args_dict)
print(func_args)
如果有来生，一个人去远行，看不同的风景，感受生命的活力。。。
