1、str.join() 2、fromkeys() 3、深浅拷贝 4、set()

1. 补充基础数据类型的相关知识点
1. str. join() 把列表变成字符串
2. 列表不能再循环的时候删除. 因为索引会跟着改变
3. 字典也不能直接循环删除.
把要删除的内容记录在列表中. 循环列表. 删除原列表, 字典中的数据
4. fromkeys() 不会对原来的字典产生影响. 产生新字典(神坑, 考试)
5. set集合. 不重复, 无序.
6. 想转换成什么.就用什么括起来
7. 深浅拷贝
1. 直接赋值. 两个变量指向同一个对象.
2. 浅拷贝:只拷贝第一层内容. copy()
3. 深度拷贝: 对象中的所有内容都会被拷贝一份
import copy
copy.deepcopy()
# # 浅拷贝 copy
# import copy
# lst = [“str1”, “str2”, “str3”, “str4”, “str5”]
# sourcelst = [“str1”, “str2”, “str3”, “str4”, “str5”, lst]
# copylst = copy.copy(sourcelst)
# print(sourcelst)
# print(copylst)
#
# sourcelst.append(“sourcestr”)
# copylst.append(“copystr”)
# print(sourcelst)
# print(copylst)
#
# sourcelst[0] = “changeSource”
# print(sourcelst)
# print(copylst)
#
# lst.append(“testAppend”)
# print(sourcelst)
# print(copylst)
#
# # 深拷贝 deepcopy
# import copy
# lst = [“str1”, “str2”, “str3”, “str4”, “str5”]
# sourcelst = [“str1”, “str2”, “str3”, “str4”, “str5”, lst]
# deepcopylst = copy.deepcopy(sourcelst)
# print(sourcelst)
# print(deepcopylst)
#
# sourcelst.append(“sourcestr”)
# deepcopylst.append(“copystr”)
# print(sourcelst)
# print(deepcopylst)
#
# sourcelst[0] = “changeSource”
# print(sourcelst)
# print(deepcopylst)
#
# lst.append(“testAppend”)
# print(sourcelst)
# print(deepcopylst)

# s = “sb”.join(“贱人”)
# print(s)

# s = [“周杰伦”, “周润发”, “麻花藤”, “周树人”]
# lis = []
# for i in s:
# if i[0] == “周”:
# lis.append(i)
# for j in lis:
# if j in s:
# s.remove(j)
# print(s)

# s = “abc”
# s1 = s.join(“非常可乐”)
# print(s1)

# s = “_”.join(([“alex”, “wuse”, “taibai”, “ritian”]))
# print(s)

# s = “sb”.join([“王者荣耀”, “LOL”, “跑跑卡丁车”])
# print(s)

# list dic 在循环的时候不能删，因为会改变索引
# lst = [“我不是药神”, “西游记”, “西红柿首富”, “天龙八部”]
# del_lst = []
# for i in lst:
# del_lst.append(i) # 记录下来要删除的内容
# for j in del_lst:
# lst.remove(j)
# print(lst)

# lst = [“周杰伦”, “周润发”, “周星星”, “马化腾”, “周树人”]
# # 删除掉姓周的人的信息
# del_lst = []
# for el in lst:
# if el.startswith(“周”):
# del_lst.append(el)
# for el in del_lst:
# lst.remove(el)
# print(lst)

# dic = {“a”: “123”, “b”: “456”}
# for k in dic:
# dic.setdefault(“c”, “123”) # 错误的
# a = dict.fromkeys([“jj”, “jay”, “taibai”, “sb”]) # 静态方法
# print(a)

# dic = {“a”: “123”}
# s = dic.fromkeys(“王健林”, “思聪”) # 返回给你一个新字典
# print(s)

# s = set() # 空集合
# dic = dict()
# s = str()
# i = int()
# lst = list()
# print(i)

# s = {“王者荣耀”, “英雄联盟”, “王者荣耀”, 123, True, True} # 集合中都是不一样的元素，输入以后会合并相同的元素
# print(s)
# s = {123, {1, 2, 3}} # 不合法
# print(s)

# lst = [“张强”, “李强”, “王磊”, “刘伟”, “张伟”, “张伟”, “刘洋”, “刘洋”]
# s = set(lst) # 去重复
# print(s)

# 变回来
# lst = list(s)
# print(lst)

# 冻结了的set集合，可哈希的，不可变
# s = frozenset([1, 3, 6, 6, 9, 8]) # 可以去重复，也是set集合
# print(s)

# ss = {“a”, s}
# print(ss)

本文链接：https://www.cnblogs.com/wjs521/p/9291960.html

1、str.join() 2、fromkeys() 3、深浅拷贝 4、set()

1、str.join() 2、fromkeys() 3、深浅拷贝 4、set()

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