Python常用知识点汇总

914次阅读  |  发布于5年以前

1、Set基本数据类型

a、set集合,是一个无序且不重复的元素集合


    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、数据类型模块举例


    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、深浅拷贝

a、数字和字符串

对于 数字 和 字符串 而言,赋值、浅拷贝和深拷贝无意义,因为其永远指向同一个内存地址。

    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、其他基本数据类型

对于字典、元祖、列表 而言,进行赋值、浅拷贝和深拷贝时,其内存地址的变化是不同的。

1、赋值

赋值,只是创建一个变量,该变量指向原来内存地址,如:


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

2、浅拷贝

浅拷贝,在内存中只额外创建第一层数据


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

3、深拷贝

深拷贝,在内存中将所有的数据重新创建一份(排除最后一层,即:python内部对字符串和数字的优化)

3、函数

函数式:将某功能代码封装到函数中,日后便无需重复编写,仅调用函数即可
面向对象:对函数进行分类和封装,让开发"更快更好更强...

.函数的定义主要有如下要点:

def:表示函数的关键字
函数名:函数的名称,日后根据函数名调用函数
函数体:函数中进行一系列的逻辑计算,如:发送邮件、计算出 [11,22,38,888,2]中的最大数等...
参数:为函数体提供数据
返回值:当函数执行完毕后,可以给调用者返回数据。

1、返回值

函数是一个功能块,该功能到底执行成功与否,需要通过返回值来告知调用者。

以上要点中,比较重要有参数和返回值:


    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...

函数的有三中不同的参数:

普通参数

######### 定义函数 #########

name 叫做函数func的形式参数,简称:形参

def func(name):
print name

######### 执行函数 #########

'zhangyanlin' 叫做函数func的实际参数,简称:实参

func('zhangyanlin')

默认参数

def func(name, age = 18):

print "%s:%s" %(name,age)  

指定参数

func('zhangyanlin', 19)

使用默认参数

func('nick')

注:默认参数需要放在参数列表最后
  

动态参数


    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

邮件实例:


    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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