【Python之路】第四篇--Python基礎之函數

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三元運算

三元運算（三目運算），是對簡單的條件陳述式的縮寫

# 書寫格式 result = 值1 if 條件 else 值2 # 如果條件成立，那麼將 “值1” 賦值給result變數，否則，將“值2”賦值給result變數

基礎資料型別 (Elementary Data Type)補充

set

set集合，是一個無序且不重複的元素集合

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. 清除內容"""        pass     def copy(self, *args, **kwargs): # real signature unknown        """ Return a shallow copy of a set. 淺拷貝  """        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.  從當前集合中刪除和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，不存在不保錯        """        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.  取交集並更更新到A中 """        pass     def isdisjoint(self, *args, **kwargs): # real signature unknown        """ Return True if two sets have a null intersection.  如果沒有交集，返回True，否則返回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，不存在保錯        """        pass     def symmetric_difference(self, *args, **kwargs): # real signature unknown        """        Return the symmetric difference of two sets as a new set.  對稱差集                 (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. 對稱差集，並更新到a中 """        pass     def union(self, *args, **kwargs): # real signature unknown        """        Return the union of sets as a new set.  並集                 (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

練習：尋找差異

#!/usr/bin/env python# -*-coding:utf-8 -*-old_dict = {    "#1":11,    "#2":22,    "#3":100,}new_dict = {    "#1":33,    "#4":22,    "#7":100,}old_set = set(old_dict.keys())new_set = set(new_dict.keys())same_set = old_set.intersection(new_set)up_set = new_set.difference(old_set)ret_dict = {}for k in same_set:    ret_dict[k]=new_dict[k]for i in up_set:    ret_dict[i]=new_dict[i]print(ret_dict)# print(old_set)# print(new_set)

深淺拷貝

一、數字和字串

對於 數字 和 字串 而言，賦值、淺拷貝和深拷貝無意義，因為其永遠指向同一個記憶體位址。

import copya = 132b = ‘Ales‘# ## 淺拷貝 ##aa = copy.copy(a)bb = copy.copy(b)# ## 深拷貝 ##aaa = copy.deepcopy(a)bbb = copy.deepcopy(b)print(id(a),id(aa),id(aaa))print(id(b),id(bb),id(bbb))# ## 1691783456   1691783456     1691783456# ##  47227376    47227376       47227376

二、其他基礎資料型別 (Elementary Data Type)

對於字典、元祖、列表 而言，進行賦值、淺拷貝和深拷貝時，其記憶體位址的變化是不同的。

1、賦值

賦值，只是建立一個變數，該變數指向原來記憶體位址，如：

n1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}  n2 = n1

2、淺拷貝

淺拷貝，在記憶體中只額外建立第一層資料

import copy  n1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}  n3 = copy.copy(n1)print(id(n1),id(n3))print(id(n1["k1"]),id(n3["k1"]))# 44947080 45383304# 45327056 45327056

3、深拷貝

深拷貝，在記憶體中將所有的資料重新建立一份（排除最後一層，即：python內部對字串和數位最佳化）

import copyn1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}n4 = copy.deepcopy(n1)print(id(n1),id(n4))print(id(n1["k3"]),id(n4["k3"]))print(id(n1["k3"][0]),id(n4["k3"][0]))# 56088200 56460680# 58962760 58930696# 56506216 56506216

函數

 

【Python之路】第四篇--Python基礎之函數