python基础，,一、python三元

python基础，,一、python三元

一、python三元运算

二、基本数据类型之集合

三、赋值和深浅拷贝

四、自定义函数的创建、调用和函数参数

五、练习

一、python三元运算

　　result = 值1 if 条件 else 值2 ：如果条件成立则result等于值1 ，否则等于值2

二、set 集合

set 是一个无序且不重复的元素集合，支持并集、交集、差集、对称差集等数学运算，set不记录元素位置，因此不支持索引，分片等操作。声名方法：

　　　　SET_NAME = set()

　　　　SET_NAME = {1,2,3,4.....} （不能用此方法创建空集合，系统会认为是创建一个空字典。）方法：

　　3.方法：

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.         从集合中移除所有元素        """        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.        返回两个或多个集合中的不同值并将这些不同值生成一个新的集合。        (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，如果元素不存在不报错        """        pass    def intersection(self, *args, **kwargs): # real signature unknown        """        Return the intersection of two sets as a new set.        返回两个集合的交集将其生成一个新的集合        (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.         如果没有交集则返回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.        移除指定元素，并返回结果        """        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，不存在不报错        """        pass    def symmetric_difference(self, *args, **kwargs): # real signature unknown        """        Return the symmetric difference of two sets as a new set.                (i.e. all elements that are in exactly one of the sets.)        对称交集        """        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.                (i.e. all elements that are in either set.)        并集        """        pass    def update(self, *args, **kwargs): # real signature unknown        """ Update a set with the union of itself and others.         更新        """        pass    def __and__(self, *args, **kwargs): # real signature unknown        """ Return self&value. """        pass    def __contains__(self, y): # real signature unknown; restored from __doc__        """ x.__contains__(y) <==> y in x. """        pass    def __eq__(self, *args, **kwargs): # real signature unknown        """ Return self==value. """        pass    def __getattribute__(self, *args, **kwargs): # real signature unknown        """ Return getattr(self, name). """        pass    def __ge__(self, *args, **kwargs): # real signature unknown        """ Return self>=value. """        pass    def __gt__(self, *args, **kwargs): # real signature unknown        """ Return self>value. """        pass    def __iand__(self, *args, **kwargs): # real signature unknown        """ Return self&=value. """        pass    def __init__(self, seq=()): # known special case of set.__init__        """        set() -> new empty set object        set(iterable) -> new set object                Build an unordered collection of unique elements.        # (copied from class doc)        """        pass    def __ior__(self, *args, **kwargs): # real signature unknown        """ Return self|=value. """        pass    def __isub__(self, *args, **kwargs): # real signature unknown        """ Return self-=value. """        pass    def __iter__(self, *args, **kwargs): # real signature unknown        """ Implement iter(self). """        pass    def __ixor__(self, *args, **kwargs): # real signature unknown        """ Return self^=value. """        pass    def __len__(self, *args, **kwargs): # real signature unknown        """ Return len(self). """        pass    def __le__(self, *args, **kwargs): # real signature unknown        """ Return self<=value. """        pass    def __lt__(self, *args, **kwargs): # real signature unknown        """ Return self<value. """        pass    @staticmethod # known case of __new__    def __new__(*args, **kwargs): # real signature unknown        """ Create and return a new object.  See help(type) for accurate signature. """        pass    def __ne__(self, *args, **kwargs): # real signature unknown        """ Return self!=value. """        pass    def __or__(self, *args, **kwargs): # real signature unknown        """ Return self|value. """        pass    def __rand__(self, *args, **kwargs): # real signature unknown        """ Return value&self. """        pass    def __reduce__(self, *args, **kwargs): # real signature unknown        """ Return state information for pickling. """        pass    def __repr__(self, *args, **kwargs): # real signature unknown        """ Return repr(self). """        pass    def __ror__(self, *args, **kwargs): # real signature unknown        """ Return value|self. """        pass    def __rsub__(self, *args, **kwargs): # real signature unknown        """ Return value-self. """        pass    def __rxor__(self, *args, **kwargs): # real signature unknown        """ Return value^self. """        pass    def __sizeof__(self): # real signature unknown; restored from __doc__        """ S.__sizeof__() -> size of S in memory, in bytes """        pass    def __sub__(self, *args, **kwargs): # real signature unknown        """ Return self-value. """        pass    def __xor__(self, *args, **kwargs): # real signature unknown        """ Return self^value. """        pass    __hash__ = None

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三、赋值和深浅拷贝

赋值：a = 3

　　　b = a

　　a,b指向同一片内存地址，可以使用id()来查看，赋值操作不会开辟新的内存空间，它只是复制了新对象的引用。在这只是增加了b这个变量名的内存。

如果想修改一个对象并且让原始对象不受影响，就需要进行复制（拷贝）操作。

数字的字符串还能被拷贝

如果元组内只包含数字或字符串则不能深拷贝

1.浅拷贝（shallow copy）：

　　创建方式：

　　　　import copy

　　　　copy.copy()

浅拷贝在内存中只额创建第一层数据。

import copyn1 = {‘k1‘:‘wu‘,‘k2‘:123;‘k3‘:[‘alex‘,456]}n3 = copy.copy(n1)

2.深拷贝：

创建方式：

　import copy

copy.deepcopy()

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内部对数字和字符串的优化。）

import copyn1 = {‘k1‘:‘wu‘,‘k2‘:123,‘k3‘:[‘alex‘,456]}n4 = copy.deepcopy(n1)

四、自定义函数的创建、调用和函数参数

函数是将一些代码组织到一起可以实现特定功能的代码块，将重复率较高的代码封装到函数中，需要时调用函数就可以实现功能。

1.自定义函数的创建

def 函数名（形参）:    函数体    ....    返回值

def:创建函数的关键字函数名：函数的名称，以后可根据函数名调用函数函数体：函数中进行一系列的逻辑运算形参：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，如果不指定默认返回None

python基础