Python学习笔记（3）-- 列表/元组/字典/集合操作
列表
mylist = ["a", "b", "c", "d", "e", "f", "g"] # 元素获取 print(mylist[0]) # 元素更新 mylist[0] = "not a" # 元素删除 del mylist[0] # 列表遍历 for e in mylist: pass # 判断元素是否在列表中 print("b" in mylist) # 列表的切片操作 print(mylist[0::1]) print(mylist[::-1]) # 倒排 # 元素添加 mylist.append("h") # 末尾添加 mylist.extend(["i", "j"]) # 合并其他列表 mylist = mylist + ["k", "l"] # 列表合并 mylist.insert(3, "new element") # 插入中间元素 print(mylist) # 列表排序 num_list = [9, 2, 4, 6, 3] num_list = sorted(num_list, reverse=True) num_list.sort(reverse=False) print(num_list)
列表的一些常用方法：
num_list = [9, 2, 4, 6, 3] other_list = [3, 9, 10] # 添加 num_list.append("new element") num_list.extend(other_list) num_list.insert(0, 100) # 删除 num_list.remove(100) num_list.pop(0) # 参数是位置index，不是元素的值 num_list.clear() # 倒序 num_list.reverse() # 枚举遍历 num_list = [9, 2, 4, 6, 3] for index, element in enumerate(num_list): print(index, element)
元组
my_tuple = (5, 2, 3, 4, 5) print(my_tuple[2]) print(my_tuple.count(5)) # 统计元素的个数 print(max(my_tuple)) # 最大值 print(min(my_tuple)) # 最小值 print(sum(my_tuple)) # 求和
拆包和装包
my_tuple = (5, 2, 3, 4, 5) a, *b, c = my_tuple print(a, b, c) # 5 [2, 3, 4] 5 print(a, *b, c) # 5 2 3 4 5
*b包含中间任意个元素。
字典
my_dict = {"a": 1, "b": 2, "c": 3}
new_dict = dict([("a", 1), ("b", 2), ("c", 3)])
print(my_dict == new_dict) # True
# 查询
print(my_dict["a"])
print(my_dict.get("b"))
# 添加
my_dict["d"] = 4
# 删除
del my_dict["d"]
value = my_dict.pop("c", "没有该值！") # 弹出该key的元素，否则返回默认值
print("result:", value)
my_dict.clear()
# 遍历
for key in my_dict:
print(key)
for key, value in my_dict.items():
print(key, value)
# 两个字典修改
my_dict = {"a": 1, "b": 2, "c": 3}
new_dict = dict([("a", 1), ("b", 2), ("c", 4)])
my_dict.update(new_dict)
print(my_dict)
集合
my_set = {"a", "b", "c", "d"}
other_set = {"a", "e"}
# 添加
my_set.add("e")
my_set.update(other_set) # 合并两个集合
# 遍历
for e in my_set:
print(e)
# 删除
my_set.remove("a")
my_set.discard("b") # 删除指定元素，remove不存在会抛异常，discard不会
my_set.pop() # 不能指定元素，弹出第一个元素
my_set.clear()
集合的交集、并集、差集和对称差集：
my_set = {"a", "b", "c", "d"}
other_set = {"a", "e"}
# 并集
new_set = my_set | other_set
new_set = my_set.union(other_set)
# 差集
new_set = my_set - other_set
new_set = my_set.difference(other_set) # {'c', 'd', 'b'}
# 交集
new_set = my_set & other_set # {'a'}
new_set = my_set.intersection(other_set)
# 对称差集
new_set = (my_set | other_set) - (my_set & other_set)
new_set = my_set ^ other_set # {'c', 'd', 'b', 'e'}
