Python common knowledge points

1. Set basic data type

a. Set collection is an unordered and non-repeating collection of elements

class set(object):
  """
  set() -> new empty set object
  set(iterable) -> new set object
   
  Build an unordered collection of unique elements.
  """
  def add(self, *args, **kwargs): # real signature unknown
    """
    Add an element to a set，添加元素
     
    This has no effect if the element is already present.
    """
    pass
 
  def clear(self, *args, **kwargs): # real signature unknown
    """ Remove all elements from this set. 清楚内容"""
    pass
 
  def copy(self, *args, **kwargs): # real signature unknown
    """ Return a shallow copy of a set. 浅拷贝 """
    pass
 
  def difference(self, *args, **kwargs): # real signature unknown
    """
    Return the difference of two or more sets as a new set. A中存在，B中不存在
     
    (i.e. all elements that are in this set but not the others.)
    """
    pass
 
  def difference_update(self, *args, **kwargs): # real signature unknown
    """ Remove all elements of another set from this set. 从当前集合中删除和B中相同的元素"""
    pass
 
  def discard(self, *args, **kwargs): # real signature unknown
    """
    Remove an element from a set if it is a member.
     
    If the element is not a member, do nothing. 移除指定元素，不存在不保错
    """
    pass
 
  def intersection(self, *args, **kwargs): # real signature unknown
    """
    Return the intersection of two sets as a new set. 交集
     
    (i.e. all elements that are in both sets.)
    """
    pass
 
  def intersection_update(self, *args, **kwargs): # real signature unknown
    """ Update a set with the intersection of itself and another. 取交集并更更新到A中 """
    pass
 
  def isdisjoint(self, *args, **kwargs): # real signature unknown
    """ Return True if two sets have a null intersection. 如果没有交集，返回True，否则返回False"""
    pass
 
  def issubset(self, *args, **kwargs): # real signature unknown
    """ Report whether another set contains this set. 是否是子序列"""
    pass
 
  def issuperset(self, *args, **kwargs): # real signature unknown
    """ Report whether this set contains another set. 是否是父序列"""
    pass
 
  def pop(self, *args, **kwargs): # real signature unknown
    """
    Remove and return an arbitrary set element.
    Raises KeyError if the set is empty. 移除元素
    """
    pass
 
  def remove(self, *args, **kwargs): # real signature unknown
    """
    Remove an element from a set; it must be a member.
     
    If the element is not a member, raise a KeyError. 移除指定元素，不存在保错
    """
    pass
 
  def symmetric_difference(self, *args, **kwargs): # real signature unknown
    """
    Return the symmetric difference of two sets as a new set. 对称交集
     
    (i.e. all elements that are in exactly one of the sets.)
    """
    pass
 
  def symmetric_difference_update(self, *args, **kwargs): # real signature unknown
    """ Update a set with the symmetric difference of itself and another. 对称交集，并更新到a中 """
    pass
 
  def union(self, *args, **kwargs): # real signature unknown
    """
    Return the union of sets as a new set. 并集
     
    (i.e. all elements that are in either set.)
    """
    pass
 
  def update(self, *args, **kwargs): # real signature unknown
    """ Update a set with the union of itself and others. 更新 """
    pass

b. Example of data type module

se = {11,22,33,44,55}
be = {44,55,66,77,88}
# se.add(66)
# print(se)  #添加元素，不能直接打印！
#
#
#
# se.clear()
# print(se)     #清除se集合里面所有的值，不能清除单个
#
#
#
# ce=be.difference(se)  #se中存在，be中不存在的值，必须赋值给一个新的变量
# print(ce)
#
#
# se.difference_update(be)
# print(se)         #在se中删除和be相同的值，不能赋值给一个新的变量，先输入转换，然后打印，也不能直接打印！
# se.discard(11)
# print(se)          #移除指定元素，移除不存在的时候，不会报错
# se.remove(11)
# print(se)       #移除指定的元素，移除不存在的会报错
# se.pop()
# print(se)        #移除随机的元素
#
#
# ret=se.pop()
# print(ret)       #移除元素，并且可以把移除的元素赋值给另一个变量
# ce = se.intersection(be)
# print(ce)    #取出两个集合的交集（相同的元素）
# se.intersection_update(be)
# print(se)    #取出两个集合的交集，并更新到se集合中
# ret = se.isdisjoint(be)
# print(ret)     #判断两个集合之间又没有交集，如果有交集返回False，没有返回True
# ret=se.issubset(be)
# print(ret)     #判断se是否是be集合的子序列，如果是返回True，不是返回Flase
# ret = se.issuperset(be)
# print(ret)     #判断se是不是be集合的父序列，如果是返回True，不是返回Flase
# ret=se.symmetric_difference(be)
# print(ret)     #对称交集，取出除了不相同的元素
# se.symmetric_difference_update(be)
# print(se)     #对称交集，取出不相同的元素并更新到se集合中
# ret = se.union(be)
# print(ret)     #并集，把两个元素集合并在一个新的变量中

##2. Dark and shallow copy

a, numbers and strings

For numbers and strings, assignment, shallow copy and deep copy are meaningless because they always point to the same memory address.

import copy
# ######### 数字、字符串 #########
n1 = 123
# n1 = "i am alex age 10"
print(id(n1))
# ## 赋值 ##
n2 = n1
print(id(n2))
# ## 浅拷贝 ##
n2 = copy.copy(n1)
print(id(n2))
  
# ## 深拷贝 ##
n3 = copy.deepcopy(n1)
print(id(n3))

# b. Other basic data types

For dictionaries, ancestors, and lists, proceed The memory address changes are different during assignment, shallow copy and deep copy.

1. Assignment

Assignment just creates a variable that points to the original memory address, such as:

n1 = {"k1": "zhangyanlin", "k2": 123, "k3": ["Aylin", 456]}
n2 = n1

2. Shallow copy

Shallow copy, only the first layer of additional data is created in the memory

import copy
n1 = {"k1": "zhangyanlin", "k2": 123, "k3": ["aylin", 456]}
n3 = copy.copy(n1)

3. Deep copy

Deep copy, recreate all the data in the memory (excluding the last layer, that is: Python's internal optimization of strings and numbers)

3. Function

Functional: Encapsulate a certain function code into a function, so there is no need to write it again in the future, just call the function

Object-oriented: Classify and encapsulate functions to make development "faster, better and stronger...

. The definition of functions mainly has the following points:

def: Keywords representing functions

Function name: The name of the function. The function will be called based on the function name in the future
Function body: A series of logical calculations are performed in the function, such as: sending emails, calculating [11,22,38,888, 2], etc...
Parameters: Provide data for the function body
Return value: When the function is executed, data can be returned to the caller.

1. Return value

The function is a function block. Whether the function is executed successfully or not, the caller needs to be informed by the return value.

Among the above points, the more important ones are parameters and return value:

def 发送短信():
    
  发送短信的代码...
  
  if 发送成功:
    return True
  else:
    return False
  
  
while True:
    
  # 每次执行发送短信函数，都会将返回值自动赋值给result
  # 之后，可以根据result来写日志，或重发等操作
  
  result = 发送短信()
  if result == False:
    短信发送失败...

The function has three different parameters:

Normal parameters

# Define function




# name is called the formal parameter of function func, abbreviated as: formal parameter
def func(name):

print name

# Execute function



# 'zhangyanlin' is called the actual parameter of function func, abbreviated as: actual parameter
func('zhangyanlin')

Default parameters

def func(name, age = 18):

   

  print "%s:%s" %(name, age)

 

# Specify Parameters

func('zhangyanlin', 19)

# Use default parameters

func('nick')

Note: The default parameters need to be placed at the end of the parameter list

Dynamic parameters

def func(*args):
 
  print args

# 执行方式一
func(11,33,4,4454,5)
 
# 执行方式二
li = [11,2,2,3,3,4,54]
func(*li)
　　

def func(**kwargs):
 
  print args
 
 
# 执行方式一
func(name＝'wupeiqi',age=18)
 
# 执行方式二
li = {'name':'wupeiqi', age:18, 'gender':'male'}
func(**li)

　def func(*args, **kwargs):
 
  print args
  print kwargs

Mail example:

def email(p,j,k):
  import smtplib
  from email.mime.text import MIMEText
  from email.utils import formataddr
 
  set = True
  try:
    msg = MIMEText('j', 'plain', 'utf-8') #j 邮件内容
    msg['From'] = formataddr(["武沛齐",'wptawy@126.com'])
    msg['To'] = formataddr(["走人",'424662508@qq.com'])
    msg['Subject'] = "k" #k主题
 
    server = smtplib.SMTP("smtp.126.com", 25)
    server.login("wptawy@126.com", "WW.3945.59")
    server.sendmail('wptawy@126.com', [p], msg.as_string())
    server.quit()
  except:
    set = False
  return True

formmail = input("请你输入收件人邮箱：")
zhuti  = input("请您输入邮件主题：")
neirong = input("请您输入邮件内容：")
aa=email(formmail,neirong,zhuti)
if aa:
  print("邮件发送成功!")
else:
  print("邮件发送失败!")

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