HackMD
effective python
tags:python
map and filter
from IPython.core.interactiveshell import InteractiveShell
InteractiveShell.ast_node_interactivity = "all"
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
squares = map(lambda x: x ** 2, a)
[x for x in squares]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
squares=filter(lambda x:x%2==0,a)
[x for x in squares]
[2, 4, 6, 8, 10]
[x**2 for x in a]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
enumerate
lolis=['loli1','loli2','loli3','loli4','loli5']
for index,value in enumerate(lolis):
print((index,value))
(0, 'loli1')
(1, 'loli2')
(2, 'loli3')
(3, 'loli4')
(4, 'loli5')
# change start from index
for index,value in enumerate(lolis,5):
print((index,value))
(5, 'loli1')
(6, 'loli2')
(7, 'loli3')
(8, 'loli4')
(9, 'loli5')
zip
brothers=["brother1","brother2","brother3","brother4"]
for i in zip(lolis,brothers):
print(i)
('loli1', 'brother1')
('loli2', 'brother2')
('loli3', 'brother3')
('loli4', 'brother4')
else after for
for i in range(2):
print(i)
if i % 2 == 0:
break
else:
print('loop finish')
0
reversed iterate
list_example = [i for i in range(5)]
iter_example = (i for i in range(5))
set_example = {i for i in range(5)}
list_example
iter_example
set_example
[0, 1, 2, 3, 4]
<generator object <genexpr> at 0x7fc7b0a6f990>
{0, 1, 2, 3, 4}
for i in reversed(list_example):
print(i)
4
3
2
1
0
for i in reversed(iter_example):
print(i)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-30-06c418582e31> in <module>()
----> 1 for i in reversed(iter_example):
2 print(i)
TypeError: argument to reversed() must be a sequence
for i in reversed(set_example):
print(i)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-31-5660da0e6339> in <module>()
----> 1 for i in reversed(set_example):
2 print(i)
TypeError: argument to reversed() must be a sequence
reversed(list_example)
<list_reverseiterator at 0x7fc7b09cb358>
class countdown(object):
def __init__(self,start):
self.start=start
def __iter__(self):
n=self.start
while n>0:
yield n
n-=1
def __reversed__(self):
n=1
while n<=self.start:
yield n
n+=1
for i in reversed(countdown(4)):
print(i)
1
2
3
4
for i in countdown(4):
print(i)
4
3
2
1
count_rev=reversed(countdown(100))
next(count_rev)
1
for/try/else
若執行try沒有發生異常，則執行else,for 則是執行時若沒有break，則會執行else
try:
print("loli OUOb")
except:
print("except occure!")
else:
print("else statment")
finally:
print("finally statement")
loli OUOb
else statment
finally statement
for x in [4,5,6,7,8]:
if x>10:
break
else:
print("Hello world!")
Hello world!
decorator
def more(fun):
def new_fun(*args,**kwargs):
print('current fun:',fun.__name__)
print('arguments"',args)
print('key arguments:',kwargs)
result=fun(*args,**kwargs)
print('result:',result)
return result
return new_fun
@more
def add(a,b):
return a+b
add(5,10)
current fun: add
arguments" (5, 10)
key arguments: {}
result: 15
15
在decorater加入參數
def read_file(filename=''):
def more(fun):
print(filename)
def new_fun(*args,**kwargs):
print('current fun:',fun.__name__)
print('arguments"',args)
print('key arguments:',kwargs)
result=fun(*args,**kwargs)
print('result:',result)
return result
return new_fun
return more
# pass argument into decorator
@read_file(filename='log.txt')
def add(a, b):
return a + b
@more
def add(a, b):
return a + b
print(add.__name__) # decorate func name wiil change
log.txt
new_fun
functools.wraps
from functools import wraps
def decorator_fun(fun):
@wraps(fun)
def new_fun(*args, **kwargs):
result = fun(*args, **kwargs)
print(result)
return result
return new_fun
@decorator_fun
def add(a, b):
return a + b
print(add.__name__)
add(5,10)
add
15
15
using the call method
from functools import wraps
class logResult(object):
def __init__(self, filename='results.txt'):
self.filename = filename
def __call__(self, fun):
@wraps(fun)
def new_fun(*args, **kwargs):
result = fun(*args, **kwargs)
with open(filename, 'a') as f:
f.write(result + '\n')
return result
self.send_notification()
return new_fun
def send_notification(self):
pass
@logResult('log.txt')
def add(a, b):
return a + b
print(add.__name__)
add
iterable
def loop(items):
for i in items:
yield i
foo = loop([1, 2, 3, 4])
for i in foo:
print(i)
# the list of generator can only be print once
# will print nothing
for i in foo:
print(i)
1
2
3
4
use itrable class to iterate again
class LoopIter(object):
def __init__(self, data):
self.data = data
def __iter__(self):
for index, letter in enumerate(self.data):
if letter == 'a':
yield index
string = 'this is a test to find a\' index'
indexs = LoopIter(string)
print('loop 1')
for _ in indexs:
print(_)
# can be print twice
print('loop 2')
for _ in indexs:
print(_)
loop 1
8
23
loop 2
8
23
but the _iter_ method can only be iterate by for loop.
If you wan't to iterate by next you have to use the iter function
string = 'this is a test to find a\' index'
indexs = LoopIter(string)
# next(indexs) # TypeError: 'LoopIter' object is not an iterator
iter_indexs = iter(indexs)
next(iter_indexs)
8
sending multiple argument into function
def square(*args):
result=0
for i in args:
result+=i**2
return result
square(1,2,3,4,5)
square(*[1,3,4,5,6,7])
55
136
關鍵字參數
def get_indexs(array, *, target='', judge=True):
for index, item in enumerate(array):
if judge and item == target:
yield index
elif not judge and item != target:
yield index
array = [1, 2, 3, 4, 1]
result = get_indexs(array, target=1, judge=True)
print(*result)
# can ignore
result = get_indexs(array, target=1)
print(*result)
0 4
0 4
you have to specfic the argument
result=get_indexs(array,1,False)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-98-de1480137b59> in <module>()
----> 1 result=get_indexs(array,1,False)
TypeError: get_indexs() takes 1 positional argument but 3 were given
default argument in function
def get_default(value=[]):
return value
result = get_default()
result.append(1)
result2 = get_default()
result2.append(2)
print(result) # [1, 2]
print(result2) # [1, 2]
[1, 2]
[1, 2]
def get_default(value=None):
if value is None:
return []
return value
result = get_default()
result.append(1)
result2 = get_default()
result2.append(2)
print(result) # [1]
print(result2) # [2]
[1]
[2]
classmethod and staticmethod__call__
class Parrotlet(object):
size=15
def __init__(self,*,name='',color=''):
self.name=name
self.color=color
def color(self):
return self.color
@staticmethod
def talk(message):
print(message)
@classmethod
def bar(clz,name,color):
print("New parrotlet!",clz.__name__)
parrot=Parrotlet(name=name,color=color)
return parrot
parrot1=Parrotlet(name='parrot1',color='green')
parrot1.size
parrot1.color
parrot1.talk("Hello world")
parrot2=parrot1.bar('parrot1','red')
parrot2.talk("parrot2 talk")
parrot2.size=20 # parrot2's attribute
assert parrot2.size!=(parrot1.size==Parrotlet.size)
Parrotlet.size=20
assert parrot2.size==parrot1.size==Parrotlet.size
15
'green'
Hello world
New parrotlet! Parrotlet
parrot2 talk
_call_ method
class Get_index(object):
def __init__(self):
pass
def __call__(self,array,target):
for index, item in enumerate(array):
if item == target:
yield index
get_index=Get_index()
print(*get_index([1,2,3,4,3,5,6],3))
2 4
split
def concat(sp="/",*args,**kwargs):
if args:
return sp.join((str(i) for i in args))
if kwargs:
for k in kwargs.keys():
print("{}{}{}".format(k,sep,kwargs[k]))
return None
concat2("~",hello="world",python="rocks")
print(concat("/",*("G",100,"cm",)))
print(concat("GGC","GCC"))
#unpacking
d={"hello":"world","python":"rocks"}
print({**d}["python"]) # get d["python"]
user={"name":"Trey",'website':"http://treyhunner.com"}
defaults={'name':"Anonymous User",'page_name':"Profile page"}
print({**defaults,**user}) # the default user name will be override
print(concat("/",*("Hello python")))
python~rocks
hello~world
G/100/cm
GCC
rocks
{'name': 'Trey', 'page_name': 'Profile page', 'website': 'http://treyhunner.com'}
H/e/l/l/o/ /p/y/t/h/o/n
bytes
print(b'python')
"""
Bytes 代表的是（二進位）數字的序列，
通過 ASCII 编碼之後才是我們看到的字符形式
"""
print("print ascii number")
print(b"Python"[0])
print(b"P"[0])
# print(b"嗨") # can only contain ASCII chacters
b'python'
print ascii number
80
80
print("print hex number when it is out of ascii range")
# convert the word out of ASCII range(31-127) to hex number
print(b'\xAF'[0])
print(b'\xaa'[0])
print(b'\xAB')
print hex number when it is out of ascii range
175
170
b'\xab'
print("convert number to ascii")
# convert number to ascii
print(bytes([24]))
print(bytes([65,60,55]))
print("convert hex to bytes")
# convert hex to bytes
print(bytes.fromhex("7A 7C"))
print(b'ASCII'.hex())
print(int(b' '.hex(), base=16)) #have space
convert number to ascii
b'\x18'
b'A<7'
convert hex to bytes
b'z|'
4153434949
32
# encode
print("A".encode('ascii'))
print("A".encode('ascii')[0])# find value in ascii
# encode by unicode
snake = '拉拉拉拉'
try:
snake.encode('ascii')
except UnicodeEncodeError as err:
print(err)
# use UTF-8
print(snake.encode()) # utf-8 by default
# bytearray is like byte "list",we can change it's
# element but can't change byte's.
ba=bytearray(b"Hello World")
ba[0:1]=b"W"
print(ba)
b'A'
65
'ascii' codec can't encode characters in position 0-3: ordinal not in range(128)
b'\xe6\x8b\x89\xe6\x8b\x89\xe6\x8b\x89\xe6\x8b\x89'
bytearray(b'Wello World')
# bytes object
b = b'example'
# str object
s = "example"
# str to bytes
bytes(s, encoding = "utf8")
# bytes to str
str(b, encoding = "utf-8")
# an alternative method
# str to bytes
str.encode(s)
# bytes to str
bytes.decode(b)
'example'
def convert_bytes_to_str(converted:bytes)->int:
return bytes(converted).decode('utf-8')
import json
string=b'{"tmst":954473276,"time":"2017-06-26T15:52:55.802041+08:00","chan":5,"rfch":0,"freq":916.200000,"stat":1,"modu":"LORA","datr":"SF7BW125","codr":"4/5","lsnr":6.8,"rssi":-41,"size":15,"data":"QHhWNBKAEAAPyKqiGZ5W"}'
json.loads(string.decode('utf-8'))
{'chan': 5,
'codr': '4/5',
'data': 'QHhWNBKAEAAPyKqiGZ5W',
'datr': 'SF7BW125',
'freq': 916.2,
'lsnr': 6.8,
'modu': 'LORA',
'rfch': 0,
'rssi': -41,
'size': 15,
'stat': 1,
'time': '2017-06-26T15:52:55.802041+08:00',
'tmst': 954473276}
context manager
from contextlib import contextmanager
import logging
def my_function():
logging.debug("Some debug data")
logging.error("Error log here")
logging.info("Info here")
@contextmanager
def debug_logging(level):
logger=logging.getLogger()
old_level=logger.getEffectiveLevel()
logger.setLevel(level)
try:
yield
finally:
logger.setLevel(old_level)
with debug_logging(logging.DEBUG):
print("Inside:")
my_function()
print("After")
my_function()
DEBUG:root:Some debug data
ERROR:root:Error log here
INFO:root:Info here
ERROR:root:Error log here
Inside:
After
_G = {"counter": 99, "user": "admin"}
class Refs():
def __init__(self, name = None):
self.name = name
self._G = _G
self.init = self._G['counter']
def __enter__(self):
return self
def __exit__(self, *args):
self._G["counter"] = self.init
return False
def acc(self, n = 1):
self._G["counter"] += n
def dec(self, n = 1):
self._G["counter"] -= n
def __str__(self):
return "COUNTER #{name}: {counter}".format(**self._G, name=self.name)
with Refs("ref1") as ref1, Refs("ref2") as ref2:
for _ in range(3):
ref1.dec()
print(ref1)
ref2.acc(2)
print(ref2)
print(_G)
COUNTER #ref1: 98
COUNTER #ref2: 100
COUNTER #ref1: 99
COUNTER #ref2: 101
COUNTER #ref1: 100
COUNTER #ref2: 102
{'user': 'admin', 'counter': 99}
Data and Time
from calendar import TextCalendar, HTMLCalendar
# calendar
tc=TextCalendar(firstweekday=6)
tc.prmonth(2016,5)
from datetime import date, time, datetime
d1=date(2016,3,29)
d2=date.today()
d3=date.fromtimestamp(_time.time())
print(d1)
print(d2)
print(d3)
May 2016
Su Mo Tu We Th Fr Sa
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31
2016-03-29
2017-06-21
2017-06-21
# get month year day
print("{}/{}/{}".format(d2.year,d2.month,d2.day))
#return struct_time struct,which can convert to tuple
print("time.struct_time: {}".format(tuple(d2.timetuple())))
print("Monday is 0: {}\nMonday is 1: {}".format(d2.weekday(), d2.isoweekday()))
2017/6/21
time.struct_time: (2017, 6, 21, 0, 0, 0, 2, 172, -1)
Monday is 0: 2
Monday is 1: 3
# Time
t1 = time(22, 57, 6, 6)
t2 = datetime.now().time()
print(t1)
print(t2)
22:57:06.000006
18:33:00.607976
# datetime.datetime
dt1 = datetime(2016, 3, 30, 22, 2)
dt2 = datetime.now()
dt3 = datetime.fromtimestamp(_time.time())
print(dt1)
print(dt2)
print(dt3)
2016-03-30 22:02:00
2017-06-21 18:33:15.273695
2017-06-21 18:33:15.273779
# combine date and time
dt = datetime.now()
dt = datetime.fromtimestamp(_time.time())
d = dt.date()
t = dt.time()
print("Date: {}\nTime: {}".format(d, t))
print("Datetime: {}".format(datetime.combine(date.today(), time(2,3,3))))
Date: 2017-06-21
Time: 18:34:31.443875
Datetime: 2017-06-21 02:03:03
# count day
from datetime import timedelta
td = timedelta(weeks=1, days=2, hours=3,minutes=4, seconds=0, microseconds=0, milliseconds=0)
print("Time duration: {}".format(td))
# minus
current=datetime.now()
today=datetime.combine(date.today(),time(0,0,0))
print("today: ",today)
td=current-today
print("{:.0f}s of Today".format(td.total_seconds()))
today=date.today()
lastyear=today.replace(year=today.year-1)
print(today-lastyear)
t1 = current.time()
t2 = time(0, 0, 0)
try:
print(t1 - t2)
except TypeError as err:
print(err)
# strftime & strptime
print(datetime.strftime.__doc__)
print(datetime.strptime.__doc__)
fmat = "%y-%m-%d"
dt = datetime.now()
s = dt.strftime(fmat)
print(s)
print(datetime.strptime(s, fmat))
fmat = "%y/%-m/%-d"
dt = datetime.now()
dt = dt - timedelta(days=22)
print(dt.strftime(fmat))
# or
print("{}/{}/{}".format(dt.strftime("%y"), dt.month, dt.day))
Time duration: 9 days, 3:04:00
today: 2017-06-21 00:00:00
67054s of Today
365 days, 0:00:00
unsupported operand type(s) for -: 'datetime.time' and 'datetime.time'
format -> strftime() style string.
string, format -> new datetime parsed from a string (like time.strptime()).
17-06-21
2017-06-21 00:00:00
17/5/30
17/5/30
decorator
# decorator example
def log(func):
def wrapper():
print("INFO: Starting {}".format(func.__name__))
func()
print("INFO: Finishing {}".format(func.__name__))
return wrapper
@log
def run():
print("Running run...")
run()
INFO: Starting run
Running run...
INFO: Finishing run
class HTML(object):
"""
Baking HTML Tags!
"""
def __init__(self, tag="p"):
print("LOG: Baking Tag <{}>!".format(tag))
self.tag = tag
def __call__(self, func):
return lambda: "<{0}>{1}</{0}>".format(self.tag, func(), self.tag)
@HTML("html")
@HTML("body")
@HTML("div")
def body():
return "Hello"
print(body())
LOG: Baking Tag <html>!
LOG: Baking Tag <body>!
LOG: Baking Tag <div>!
<html><body><div>Hello</div></body></html>
# 傳遞參數
RULES = {}
def route(rule): # rule is a string
def decorator(hand): # hand is a function
RULES.update({rule: hand}) # 填充到RULES裡面
return hand
return decorator
@route("/")
def index():
print("Hello world!")
def home():
print("Welcome Home!")
# 將/home 和home()放進RULES
home = route("/home")(home)
index()
home()
print(RULES) # 印出RULES dict的內容
@route("/login")
def login(user="user", pwd="pwd"):
print("DB.findOne({{{}, {}}})".format(user, pwd))
login("hail", "python")
print(RULES)
Hello world!
Welcome Home!
{'/home': <function home at 0x7fd11facaa60>, '/': <function index at 0x7fd11faca840>}
DB.findOne({hail, python})
{'/home': <function home at 0x7fd11facaa60>, '/': <function index at 0x7fd11faca840>, '/login': <function login at 0x7fd11fa3f400>}
# sending paramerter
def log(f):
def wraper(*args, **kargs):
print("INFO: Start Logging")
f(*args, **kargs)
print("INFO: Finish Logging")
return wraper
@log
def run(hello="world"):
print("Hello {}".format(hello))
run("Python2")
INFO: Start Logging
Hello Python2
INFO: Finish Logging
from functools import update_wrapper
"""
functools.update_wrapper(wrapper, wrapped[, assigned][, updated])
"""
class HTML(object):
"""
Baking HTML Tags!
"""
def __init__(self, tag="p"):
print("LOG: Baking Tag <{}>!".format(tag))
self.tag = tag
def __call__(self, func):
def wraper():
return "<{0}>{1}</{0}>".format(self.tag, func(), self.tag)
update_wrapper(wraper, func)
return wraper
@HTML("body")
def body():
"""
return body content!
"""
return "Hello, body!"
print(body.__name__)
print(body.__doc__)
print(body())
LOG: Baking Tag <body>!
body
return body content!
<body>Hello, body!</body>
# 利用partial 修飾
from functools import update_wrapper, partial
def my_wraps(wrapped):
print(update_wrapper,wrapped)
return partial(update_wrapper, wrapped=wrapped)
def log(func):
@my_wraps(func)
def wraper():
print("INFO: Starting {}".format(func.__name__))
func()
print("INFO: Finishing {}".format(func.__name__))
return wraper
@log
def run():
"""
Docs' of run
"""
print("Running run...")
print(run.__name__)
print(run.__doc__)
print(run())
<function update_wrapper at 0x7fd1515ebd08> <function run at 0x7fd11fa84510>
run
Docs' of run
INFO: Starting run
Running run...
INFO: Finishing run
None
heap and queue
from heapq import heapify,heappop,heappush
print(heapq.__all__)
heap=[]
heappush(heap,3)
heappush(heap,2)
heappush(heap,1)
print(heap)
# use heapify to turn list to heap
heap=list(reversed(range(5)))
print("List: ",heap)
heapify(heap)
print("Heap: ",heap)
# heap 每次pop 出來的元素都會是最小的
heap=[2,3,4,1,2,4,6,7,11]
heapify(heap)
print(heappop(heap))
print(heappop(heap))
print(heappop(heap))
print(heappop(heap))
print(heap)
['heappush', 'heappop', 'heapify', 'heapreplace', 'merge', 'nlargest', 'nsmallest', 'heappushpop']
[1, 3, 2]
List: [4, 3, 2, 1, 0]
Heap: [0, 1, 2, 4, 3]
1
2
2
3
[4, 6, 4, 7, 11]
queue
# queue.PriorityQueue
from queue import PriorityQueue as PQueue
pq=PQueue()
pq.put((5*-1,'Python'))
pq.put((4*-1,'C'))
pq.put((4,'JS'))
pq.put((3*-1,'Java'))
pq.put((2*-1,'C++'))
print('Inside PriorityQueue: ',pq.queue)
while not pq.empty():
print(pq.get()[1])
Inside PriorityQueue: [(-5, 'Python'), (-4, 'C'), (4, 'JS'), (-3, 'Java'), (-2, 'C++')]
Python
C
Java
C++
JS
# 經過list.sort()的list一定是heap 反之未必,只有經過heapify()的heap 才是heap
# 而經過heappush()和heappop()都會對heap進行重新整理
import random
from heapq import nlargest,nsmallest
rand_list = [random.randrange(1, 100) for _ in range(5)]
rand_list.sort()
print("List: ", rand_list)
print("Poped: ", heappop(rand_list))
heappush(rand_list, 4)
print("Heap: ", rand_list)
print("N largest: ",nlargest(10,heap))
print("N smallest: ",nsmallest(10,heap))
print(len(heap))
List: [19, 37, 45, 83, 85]
Poped: 19
Heap: [4, 37, 45, 85, 83]
N largest: [11, 7, 6, 4, 4]
N smallest: [4, 4, 6, 7, 11]
5
# merge heap
from heapq import merge
heapA = sorted([random.randrange(1, 100) for _ in range(3)])
heapB = sorted([random.randrange(1, 100) for _ in range(3)])
print(heapA)
print(heapB)
merged = []
for i in merge(heapA, heapB):
merged.append(i)
print(merged)
[18, 61, 85]
[14, 47, 75]
[14, 18, 47, 61, 75, 85]
# heappushpop and heap replace
from heapq import heapreplace,heappushpop
lstA = [1,2,3,4,5]
lstB = [1,2,3,4,5]
poped = heapreplace(lstA, 0)
print("lstA: ", lstA, "poped: ", poped)
# pop and push
poped = heappop(lstB)
heappush(lstB, 0)
print("lstB: ", lstA, "poped: ", poped)
print("*"*30)
poped = heappushpop(lstA, 9)
print("lstA: ", lstA, "poped: ", poped)
# is equal to...
heappush(lstB, 9)
poped = heappop(lstB)
print("lstB: ", lstB, "poped: ", poped)
lstA: [0, 2, 3, 4, 5] poped: 1
lstB: [0, 2, 3, 4, 5] poped: 1
******************************
lstA: [2, 4, 3, 9, 5] poped: 0
lstB: [2, 4, 3, 5, 9] poped: 0
_hash_ and _eq_
class Point:
def __init__(self, x, y):
self.x = x
self.y = y
def __eq__(self, that):
if not isinstance(that, Point):
return False
return self.x == that.x and self.y == that.y
def __hash__(self):
return 41 * (41 + self.x) + self.y
p1 = Point(1, 1)
p2 = Point(1, 1)
pset = {p1}
print(p2 in pset)
class Point:
def __init__(self, x, y):
self.x = x
self.y = y
def __eq__(self, that):
if not isinstance(that, Point):
return False
return self.x == that.x and self.y == that.y
class Point3D(Point):
def __init__(self, x, y, z):
super(Point3D, self).__init__(x, y)
self.z = z
def __eq__(self, that):
if not isinstance(that, Point3D):
return False
return super(Point3D, self).__eq__(that) and self.z == that.z
p1 = Point(1, 1)
p2 = Point3D(1, 1, 1)
print(p1 == p2)
True
False
property
class Ball:
def __init__(self, radius):
if radius <= 0:
raise ValueError('must be integer')
self.__radius = radius
def getRadius(self):
return self.__radius
def setRadius(self, radius):
self.__radius = radius
def delRadius(self):
del self.__radius
radius = property(getRadius, setRadius, delRadius, 'radius blablabla')
ball=Ball(12)
print (ball.radius)
ball.radius=123
print (ball.radius)
import math
class Ball:
def __init__(self, radius):
if radius <= 0:
raise ValueError('must be integer')
self.__radius = radius
@property
def radius(self):
return self.__radius
@property
def volumn(self):
return 4.0 / 3.0 * math.pi * self.__radius ** 3
@volumn.setter
def volumn(self, volumn):
if volumn <= 0:
raise ValueError('must be integer')
self.__radius = ((3.0 * volumn) / (4.0 * math.pi)) ** (1.0 / 3.0)
ball = Ball(10.0)
print(ball.volumn)
ball.volumn = 5000
print(ball.radius)
12
123
4188.790204786391
10.60784417947055
profile
sending email by python
import smtplib
GMAIL_USER = 'EMAILADDRSS@gmail.com'
GMAIL_PASS = 'PASSWORD'
SMTP_SERVER = 'smtp.gmail.com'
SMTP_PORT = 587
def send_email(recipient, subject, text):
smtpserver = smtplib.SMTP(SMTP_SERVER,SMTP_PORT)
smtpserver.ehlo() #
smtpserver.starttls() #
smtp.ehlo #
smtpserver.login(GMAIL_USER, GMAIL_PASS)
header = 'TO:' + recipient + '\n' + 'From:' + GMAIL_USER
msg = header + '\n' + text +'\n\n'
smtpserver.sendmail(GMAIL_USER, recipient, msg)
smtpserver.close()
shallow copy and deep copy
lst=[1,2,3]
# copy list in four ways
llst=[lst[:],lst,lst.copy(),[*lst]]
print(id(lst))
print(llst[0] is lst)
print(llst[1] is lst)
print(llst[2] is lst)
print(llst[3] is lst)
for i,v in enumerate(llst):
v.append("#{}".format(i))
print(lst)
140245585483016
False
True
False
False
[1, 2, 3, '#1']
d={"a":0}
dd=[d,d.copy(),{**d}]
for i,v in enumerate(dd):
v['dd']="#{}".format(i)
print(d)
{'dd': '#0', 'a': 0}
list_tmp=[1,3,4]
llist=lst[:]
llist.append("Wifi!!!!")
print(list_tmp)
[1, 3, 4]
list_tmp=[1,3,4]
llist=list_tmp
llist.append("Wifi!!!!")
print(list_tmp)
[1, 3, 4, 'Wifi!!!!']
list_tmp=[1,3,4]
llist=lst.copy()
llist.append("Wifi!!!!")
print(list_tmp)
[1, 3, 4]
list_tmp=[1,3,4]
llist=[*[list_tmp]]
llist.append("Wifi!!!!")
print(list_tmp)
[1, 3, 4]
# shallow copy
d={"a":{"b":[0]}}
dd=[d,d.copy(),{**d}]
print(dd[0] is d)
print(dd[1] is d)
print(dd[2] is d)
True
False
False
# deepcopy
from copy import deepcopy
# list
lst=[0,1,[2,3]]
lst2=deepcopy(lst)
lst2[2].append(4)
print(lst2)
print(lst)
# dict
d={"a":{"b":[0]}}
d2=deepcopy(d)
d2["a"]["b"].append(1)
print(d2)
print(d)
[0, 1, [2, 3, 4]]
[0, 1, [2, 3]]
{'a': {'b': [0, 1]}}
{'a': {'b': [0]}}
String format
print("{lang}.{suffix}".format(**{"lang":"Python","suffix":"py"}))
print("{} {}".format(*["Python","C++"]))
data={'name':'Python','score':100}
print("Name:{0[name]}, Score:{0[score]}".format(data))
langs=["Hello","hello!"]
print("{0[0]} vs {0[1]}".format(langs))
print("\n=======\nHelp(format):\n{.__doc__}".format(str.format))
Python.py
Python C++
Name:Python, Score:100
Hello vs hello!
=======
Help(format):
S.format(*args, **kwargs) -> str
Return a formatted version of S, using substitutions from args and kwargs.
The substitutions are identified by braces ('{' and '}').
#可以通共！＋r|s|a的方式對替換的變量進行轉換：
#"{!r}"對變量調用repr()
#"{!s}"對變量調用str()
#"{!a}"對變量調用ascii()
#align 代表方向
#fill為填充的字符（默認空白）
for align, text in zip("<^>",["left","center","right"]):
print("{:{fill}{align}16}".format(text, fill=align,align=align))
print("{:0=10}".format(100))
left<<<<<<<<<<<<
^^^^^center^^^^^
>>>>>>>>>>>right
0000000100
#強制顯示正負號
print("{0:+}\n{1:-}\n{0: }".format(3.14, -3.14))
+3.14
-3.14
3.14
# 用於表示特殊格式的（二進位to十進位）是否需要符號
print("Binary: {0:b}->{0:#b}".format(3))
Binary: 11->0b11
# 表示,
print("Large Number: {0:}->{0:,}".format(1.25e5))
Large Number: 125000.0->125,000.0
# 0靠右對齊補0
print("Padding: {0:16}->{0:016}".format(3))
Padding: 3->0000000000000003
# 小數點格式優化
from math import pi
print("pi={pi:.2},also={pi:.7}".format(pi=pi))
pi=3.1,also=3.141593
# Integer
for t in "b c d #o #x #X n".split():
print("Type {0:>2} of {1} shows:{1:{t}}".format(t,97,t=t))
print("---------------------------------------------------------")
Type b of 97 shows:1100001
Type c of 97 shows:a
Type d of 97 shows:97
Type #o of 97 shows:0o141
Type #x of 97 shows:0x61
Type #X of 97 shows:0X61
Type n of 97 shows:97
---------------------------------------------------------
# Float
for t,n in zip("eEfFgGn%",[1234,123,2.3,22.11,1,2,3.1415,0.98886]):
print("Type {} shows:{:.2{t}}".format(t,n,t=t))
Type e shows:1.23e+03
Type E shows:1.23E+02
Type f shows:2.30
Type F shows:22.11
Type g shows:1
Type G shows:2
Type n shows:3.1
Type % shows:98.89%
# string
# 如果數字要印出來不用+s
try:
print("{:s}".format(1234555))
except:
print("{}".format(12345))
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-51-15f35bbfb6a3> in <module>()
2 # 如果數字要印出來不用+s
3
----> 4 print("{:s}".format(1234555))
ValueError: Unknown format code 's' for object of type 'int'
String functions
hello = [i.upper()for i in 'hello']
s = u'你好'
print(s)
print(len(s))
print(s.encode())
你好
2
b'\xe4\xbd\xa0\xe5\xa5\xbd'
"""
unicode common func
"""
str1 = "Hello World"
print(",".join(str1.split()))
print("http://www.google.com".split("/", 2)) # 限定切分切兩次
str2 = "coffee"
print(str2.find('f'))
print(str2.index('f')) # where the index is
print(str2.rfind('f')) # find from right
print(str2.find('a'))
print(str2.rfind('a'))
# print(str2.index('a')) # if not in substring than raise ValueError
Hello,World
['http:', '', 'www.google.com']
2
2
3
-1
-1
"""
stripe
"""
print(" hello world ".strip())
print("helloworld".strip("heo"))
print("[" + " i ".lstrip() + "]")
print("[" + " i ".rstrip() + "]")
print("[" + " i ".strip() + "]")
print("{}\n{}\n{}\n{}\n{}".format(
"hello, WORLD".upper(),
"hello, WORLD".lower(),
"hello, WORLD".swapcase(),
"hello, WORLD".capitalize(),
"hello, WORLD".title()))
hello world
lloworld
[i ]
[ i]
[i]
HELLO, WORLD
hello, world
HELLO, world
Hello, world
Hello, World
print("""
{}|{}
{}|{}
{}|{}
{}|{}
{}|{}
{}|{}
""".format(
"Python".startswith("P"), "Python".startswith("y"),
"Python".endswith("n"), "Python".endswith("o"),
"i23o6".isalnum(), "1 2 3 0 6".isalnum(),
"isalpha".isalpha(), "isa1pha".isalpha(),
"python".islower(), "Python".islower(),
"PYTHON".isupper(), "Python".isupper(),
))
print("HIHI".zfill(8)) # 回傳以 0 塞滿 width 的新字串
True|False
True|False
True|False
True|False
True|False
True|False
0000HIHI
sorted
#Python 提供兩種排序方法,一種是針對List的原地排序list.sort()另一個是針對所有可迭代對象的sorted()
from random import randrange
lst=[randrange(1,100) for _ in range(10)]
print(lst)
lst.sort()
print(lst)
[16, 73, 80, 49, 30, 57, 19, 38, 80, 53]
[16, 19, 30, 38, 49, 53, 57, 73, 80, 80]
#sorted() 不限於list,且會生成一個新的排序後的list,原有對象不受影響
lst=[randrange(1,100) for _ in range(10)]
tup=tuple(lst)
print(sorted(lst))
print(tup)
print(sorted(tup))
[4, 25, 58, 65, 66, 67, 72, 76, 89, 94]
(72, 58, 67, 4, 65, 89, 76, 66, 94, 25)
[4, 25, 58, 65, 66, 67, 72, 76, 89, 94]
#透過key 指定排序
lst2=[randrange(1,100) for _ in range(10)]
print(lst2)
print(sorted(lst2,key=abs)) # 透過絕對值進行排序
[93, 36, 9, 67, 86, 55, 19, 23, 30, 84]
[9, 19, 23, 30, 36, 55, 67, 84, 86, 93]
# 當迭代對象教複雜時 可以只按照其中的某些屬性進行排序
lst3=list(zip("Today is a good day,so I have to go to school.".split(),[randrange(1,10) for _ in range(13)]))
print(lst3)
print(sorted(lst3,key=lambda item:item[1])) # 透過key進行排序（可改0)
[('Today', 3), ('is', 3), ('a', 4), ('good', 6), ('day,so', 3), ('I', 3), ('have', 3), ('to', 7), ('go', 1), ('to', 8), ('school.', 1)]
[('go', 1), ('school.', 1), ('Today', 3), ('is', 3), ('day,so', 3), ('I', 3), ('have', 3), ('a', 4), ('good', 6), ('to', 7), ('to', 8)]
# 可以過operator 獲取元素的屬性
from operator import itemgetter, attrgetter
print("-"*20)
print(sorted(lst3, key=itemgetter(1)))
--------------------
[('go', 1), ('school.', 1), ('Today', 3), ('is', 3), ('day,so', 3), ('I', 3), ('have', 3), ('a', 4), ('good', 6), ('to', 7), ('to', 8)]
# 和lambda item:item[1]))作用相同
fitemgetter=lambda ind:lambda item: item[ind]
print(sorted(lst3,key=fitemgetter(1)))
class P(object):
def __init__(self, w, n):
self.w=w
self.n=n
def __repr__(self):
return "{}=>{}".format(self.w, self.n)
ps=[P(i[0],i[1]) for i in lst3]
print(sorted(ps,key=attrgetter('n')))
[('go', 1), ('school.', 1), ('Today', 3), ('is', 3), ('day,so', 3), ('I', 3), ('have', 3), ('a', 4), ('good', 6), ('to', 7), ('to', 8)]
[go=>1, school.=>1, Today=>3, is=>3, day,so=>3, I=>3, have=>3, a=>4, good=>6, to=>7, to=>8]
# python3 cmp using
from functools import cmp_to_key as new_cmp_to_key
#new_cmp_to_key work like this
def cmp_to_key(mycmp):
# convert a cmp= function into a kye= function
class K:
def __init__(self,obj,*args):
self.obj=obj
def __lt__(self, other):
return mycmp(self.obj, other.obj)
return K
def reverse_cmp(x, y):
return y[1]-x[1]
print(sorted(lst3,key=cmp_to_key(reverse_cmp)))
[('to', 8), ('go', 1), ('school.', 1), ('to', 7), ('good', 6), ('a', 4), ('Today', 3), ('is', 3), ('day,so', 3), ('I', 3), ('have', 3)]
testdoc
"""
This is the "example" module.
The example module supplies one function, factorial(). For example,
>>> factorial(5)
120
"""
def factorial(n):
"""Return the factorial of n, an exact integer >= 0.
If the result is small enough to fit in an int, return an int.
Else return a long.
>>> [factorial(n) for n in range(6)]
[1, 1, 2, 6, 24, 120]
>>> [factorial(long(n)) for n in range(6)]
[1, 1, 2, 6, 24, 120]
>>> factorial(30)
265252859812191058636308480000000L
>>> factorial(30L)
265252859812191058636308480000000L
>>> factorial(-1)
Traceback (most recent call last):
...
ValueError: n must be >= 0
Factorials of floats are OK, but the float must be an exact integer:
>>> factorial(30.1)
Traceback (most recent call last):
...
ValueError: n must be exact integer
>>> factorial(30.0)
265252859812191058636308480000000L
It must also not be ridiculously large:
>>> factorial(1e100)
Traceback (most recent call last):
...
OverflowError: n too large
"""
import math
if not n >= 0:
raise ValueError("n must be >= 0")
if math.floor(n) != n:
raise ValueError("n must be exact integer")
if n+1 == n: # catch a value like 1e300
raise OverflowError("n too large")
result = 1
factor = 2
while factor <= n:
result *= factor
factor += 1
return result
if __name__ == "__main__":
import doctest
doctest.testmod()
**********************************************************************
File "__main__", line 18, in __main__.factorial
Failed example:
[factorial(long(n)) for n in range(6)]
Exception raised:
Traceback (most recent call last):
File "/usr/lib/python3.5/doctest.py", line 1321, in __run
compileflags, 1), test.globs)
File "<doctest __main__.factorial[1]>", line 1, in <module>
[factorial(long(n)) for n in range(6)]
File "<doctest __main__.factorial[1]>", line 1, in <listcomp>
[factorial(long(n)) for n in range(6)]
NameError: name 'long' is not defined
**********************************************************************
File "__main__", line 20, in __main__.factorial
Failed example:
factorial(30)
Expected:
265252859812191058636308480000000L
Got:
265252859812191058636308480000000
**********************************************************************
File "__main__", line 22, in __main__.factorial
Failed example:
factorial(30L)
Exception raised:
Traceback (most recent call last):
File "/usr/lib/python3.5/doctest.py", line 1321, in __run
compileflags, 1), test.globs)
File "<doctest __main__.factorial[3]>", line 1
factorial(30L)
^
SyntaxError: invalid syntax
**********************************************************************
File "__main__", line 34, in __main__.factorial
Failed example:
factorial(30.0)
Expected:
265252859812191058636308480000000L
Got:
265252859812191058636308480000000
**********************************************************************
1 items had failures:
4 of 8 in __main__.factorial
***Test Failed*** 4 failures.
signal
import signal,functools
import time
class TimeoutError(Exception): pass
def timeout(seconds, error_message = 'Function call timed out'):
def decorated(func):
def _handle_timeout(signum, frame):
raise TimeoutError(error_message)
def wrapper(*args, **kwargs):
signal.signal(signal.SIGALRM, _handle_timeout)
signal.alarm(seconds)
try:
result = func(*args, **kwargs)
finally:
signal.alarm(0)
return result
return functools.wraps(func)(wrapper)
return decorated
@timeout(10,"hello world!")
def loop():
while(1):
time.sleep(5)
loop()
---------------------------------------------------------------------------
TimeoutError Traceback (most recent call last)
<ipython-input-73-6e8efc94b623> in <module>()
22 while(1):
23 time.sleep(5)
---> 24 loop()
<ipython-input-73-6e8efc94b623> in wrapper(*args, **kwargs)
11 signal.alarm(seconds)
12 try:
---> 13 result = func(*args, **kwargs)
14 finally:
15 signal.alarm(0)
<ipython-input-73-6e8efc94b623> in loop()
21 def loop():
22 while(1):
---> 23 time.sleep(5)
24 loop()
<ipython-input-73-6e8efc94b623> in _handle_timeout(signum, frame)
6 def decorated(func):
7 def _handle_timeout(signum, frame):
----> 8 raise TimeoutError(error_message)
9 def wrapper(*args, **kwargs):
10 signal.signal(signal.SIGALRM, _handle_timeout)
TimeoutError: hello world!
