None用法+连接字符串优先使用join +用format而不是%+区别可变对象和不可变对象（list的深拷贝和浅拷贝）

2. None这个东东

# 判断list是否为空list = []if list is None:                # 错误的方式    print("list is None")else:    print("list is not None")if list:                        # 正确的方式    print("list is not None")else:    print("list is None")"""output:list is not Nonelist is None"""
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3. 连接字符串优先使用join而不是+

原因：

str1, str2, str3, str4, str5 = 'my', 'heart', 'will', 'go', 'on'combine_str = ''.join([str1, str2, str3, str4, str5])print(combine_str)"""output:myheartwillgoon"""
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4. 用format而不是%

 

weather = ['a', 'b', 'c']formatter = 'letter is: {0}'.formatfor item in map(formatter, weather):    print(item)"""output:letter is: aletter is: bletter is: c""" 
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注意：

list深拷贝和浅拷贝

list1=['a','b','c']list2=list1list1.append('d')list2['a', 'b', 'c', 'd']import copylist3=copy.deepcopy(list1)list3['a', 'b', 'c', 'd']list3.append('e')list3['a', 'b', 'c', 'd', 'e']list2['a', 'b', 'c', 'd']list1['a', 'b', 'c', 'd']list1.append('f')list1['a', 'b', 'c', 'd', 'f']list2['a', 'b', 'c', 'd', 'f']list3['a', 'b', 'c', 'd', 'e']

deepcopy的作用相当于是把list3与list2、list1完全隔开了。

append表示，list1和list2是完全等同的。