Python 関数クラスの糖衣構文

s = ''
s += 'a' + \
     'b' + \
     'c'
n = 1 + 2 + \
3
# 6

num = [1,2,3,4]
mark = 0while mark < len(num):
    n = num[mark]    if n % 2 == 0:   
     print(n)        # break
    mark += 1else: print("done")

a = [1,2,3]
b = ['one','two','three']
list(zip(a,b))
# [(1, 'one'), (2, 'two'), (3, 'three')]

x = [num for num in range(6)]
# [0, 1, 2, 3, 4, 5]
y = [num for num in range(6) if num % 2 == 0]
# [0, 2, 4]

# 多层嵌套
rows = range(1,4)
cols = range(1,3)
for i in rows:
    for j in cols:
        print(i,j)
# 同
rows = range(1,4)
cols = range(1,3)
x = [(i,j) for i in rows for j in cols]

#查询每个字母出现的次数。
strs = 'Hello World'
s = { k : strs.count(k) for k in set(strs) }

>>> num = ( x for x in range(5) )>>> num
...:<generator object <genexpr> at 0x7f50926758e0>

def do(a=0,b,c)
    return (a,b,c)

do(a=1,b=3,c=2)

def buygy(arg, result=[]):
    result.append(arg)
    print(result)

def nobuygy(arg, result=None):
    if result == None:
        result = []
    result.append(arg)
    print(result)
# or
def nobuygy2(arg):
    result = []
    result.append(arg)
    print(result)

def do(*args):
    print(args)
do(1,2,3)
(1,2,3,'d')

def do(**kwargs):
  print(kwargs)
do(a=1,b=2,c='la')
# {'c': 'la', 'a': 1, 'b': 2}

a = lambda x: x*x
a(4)
# 16

def my_range(first=0,last=10,step=1):
    number = first
    while number < last:
        yield number
        number += step

>>> my_range()
... <generator object my_range at 0x7f02ea0a2bf8>

# 一个装饰器
def document_it(func):
    def new_function(*args, **kwargs):
        print("Runing function: ", func.__name__)
        print("Positional arguments: ", args)
        print("Keyword arguments: ", kwargs)
        result = func(*args, **kwargs)
        print("Result: " ,result)
        return result
    return new_function

# 人工赋值
def add_ints(a, b):
    return a + b

cooler_add_ints = document_it(add_ints) #人工对装饰器赋值
cooler_add_ints(3,5)

# 函数器前加装饰器名字
@document_it
def add_ints(a, b):
    return a + b

a = 1234
def test():
    print("a = ",a) # True
####
a = 1234
def test():
    a = a -1    #False
    print("a = ",a)

a = 1234
def test():
    global a
    a = a -1    #True
    print("a = ",a)

def amazing():
    '''This is the amazing.
    Hello
    world'''
    print("The function named: ", amazing.__name__)
    print("The function docstring is: \n", amazing.__doc__)

>>> l = [1,2,3]
>>> index = 5
>>> l[index]
Traceback (most recent call last):
  File "<stdin>", line 1, in 
  <module>IndexError: list index out of range

>>> l = [1,2,3]
>>> index = 5
>>> try:
...     l[index]
... except:
...     print("Error: need a position between 0 and", len(l)-1, ", But got", index)
...
Error: need a position between 0 and 2 , But got 5

hort_list = [1,2,3]while 1:
    value = input("Position [q to quit]? ")    if value == 'q':        break
    try:
        position = int(value)
        print(short_list[position])    except IndexError as err:
        print("Bad index: ", position)    except Exception as other:
        print("Something else broke: ", other)

class UppercaseException(Exception):
    pass

words = ['a','b','c','AA']
for i in words:
    if i.isupper():
        raise UppercaseException(i)
# error
Traceback (most recent call last):
  File "<stdin>", line 3, in <module>
__main__.UppercaseException: AA

import sys
print(sys.argv)

class Person():
    def __init__(self, name):
        self.name = nameclass email(Person):
    def __init__(self, name, email):
        super().__init__(name)
        self.email = email

a = email('me', 'me@me.me')>>> a.name... 'me'>>> a.email... 'me@me.me'

class Person():
    def __init__(self, name):
        self.__name = name
a = Person('me')>>> a.name... AttributeError: 'Person' object has no attribute '__name'# 小技巧a._Person__name

class A():
    count = 2
    def __init__(self): # 这就是一个实例方法
        A.count += 1

class A():
    count = 2
    def __init__(self):
        A.count += 1    @classmethod
    def hello(h):
        print("hello",h.count)

class A():    @staticmethod
    def hello():
        print("hello, staticmethod")
>>> A.hello()

class word():
    def __init__(self, text):
        self.text = text
    def equals(self, word2): #注意
        return self.text.lower() == word2.text.lower()
a1 = word('aa')
a2 = word('AA')
a3 = word('33')
a1.equals(a2)
# True

class word():
    def __init__(self, text):
        self.text = text    def __eq__(self, word2): #注意，使用__eq__
        return self.text.lower() == word2.text.lower()
a1 = word('aa')
a2 = word('AA')
a3 = word('33')
a1 == a2# True

*方法名*                        *使用*
__eq__(self, other)            self == other
__ne__(self, other)            self != other
__lt__(self, other)            self < other
__gt__(self, other)            self > other
__le__(self, other)            self <= other
__ge__(self, other)            self >= other

__add__(self, other)        self + other
__sub__(self, other)        self - other
__mul__(self, other)        self * other
__floordiv__(self, other)    self // other
__truediv__(self, other)        self / other
__mod__(self, other)        self % other
__pow__(self, other)        self ** other

__str__(self)                str(self)
__repr__(self)                repr(self)
__len__(self)                len(self)

'%-10d | %-10f | %10s | %10x' % ( 1, 1.2, 'ccc', 0xf )
#
'1          | 1.200000   |        ccc |         33'

'{} {} {}'.format(11,22,33)
# 11 22 33
'{2:2d} {0:-10d} {1:10d}'.format(11,22,33)
# :后面是格式标识符
# 33 11 22

'{a} {b} {c}'.format(a=11,b=22,c=33)