Python常用命令之集合

• 判断数据项是否存在list

thislist = ["apple", "banana", "cherry"]
if "apple" in thislist:
  print("Yes, 'apple' is in the fruits list")

• 遍历list

  thislist = ["apple", "banana", "cherry"]
  for x in thislist:
  print(x)

获取list长度

thislist = ["apple", "banana", "cherry"]
print(len(thislist))

追加元素

thislist = ["apple", "banana", "cherry"]

thislist.append("orange")

print(thislist)

添加固定位置

thislist = ["apple", "banana", "cherry"]
thislist.insert(1, "orange")
print(thislist)

删除某元素【只删除一个】

thislist = ["apple", "banana", "cherry"]
thislist.remove("banana")
print(thislist)

移除最后一个元素

thislist = ["apple", "banana", "cherry"]
thislist.pop()
print(thislist)

清空List

thislist = ["apple", "banana", "cherry"]
thislist.clear()
print(thislist)

修改元组值

x = ("apple", "banana", "cherry")
y = list(x)
y[1] = "kiwi"
x = tuple(y)

print(x)

声明元组

thistuple = ("apple",)
print(type(thistuple))

#NOT a tuple type is str
thistuple = ("apple")

合并元组Tuple 【不会去重】

tuple1 = ("a", "b" , "c")
tuple2 = (1, 2, 3)

tuple3 = tuple1 + tuple2
print(tuple3)

构造元组【2个括号】

thistuple = tuple(("apple", "banana", "cherry")) # note the double round-brackets
print(thistuple)

声明Set

thisset = {"apple", "banana", "cherry"}
print(thisset)

Set添加元素

thisset = {"apple", "banana", "cherry"}

thisset.add("orange")

print(thisset)

批量添加

thisset = {"apple", "banana", "cherry"}

thisset.update(["orange", "mango", "grapes"])

print(thisset)

Set 删除元素

thisset = {"apple", "banana", "cherry"}
//不存在  抛异常
thisset.remove("banana")
//不存在  不抛异常
thisset.discard("banana")

// 不知道删的内容
x = thisset.pop()

print(thisset)

合并set 内容

set1 = {"a", "b" , "c"}
set2 = {1, 2, 3}

set3 = set1.union(set2)
print(set3)

合并set 内容(不需要新变量）

set1 = {"a", "b" , "c"}
set2 = {1, 2, 3}

set1.update(set2)
print(set1)

声明set

thisset = set(("apple", "banana", "cherry")) # note the double round-brackets
print(thisset)

Dictionary

创建字典

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}

访问字段元素

# 如果没有值，异常
x = thisdict["mod1el"]
print(x)

# 如果没有值，返回None
x = thisdict.get("mo1del")
print(x)

输出字典的值

for x in thisdict.values():
  print(x)

输出字典的k,v

for x, y in thisdict.items():
  print(x, y)

复制 Dictionary

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
mydict = thisdict.copy()
print(mydict)