集合+檔案操作(1)r部分
阿新 • • 發佈:2020-12-24
昨日補充:
####d.update():更新,無就新增,有就覆蓋 d={"name":"egon","age":18,"gender":"xxxx"} res = d.update({"gender":"male"}) print(d)>>>>>{'name': 'egon', 'age': 18, 'gender': 'male'} print(res)>>>>None ####d.setdefault():有就不變,無才新增 res = d.setdefault("gender","male") print(res)>>>>>>>xxxx`` print(d)>>>>>{'name': 'egon', 'age': 18, 'gender': 'xxxx'}
取交集(麻煩的辦法)
pythons = ["tom","jack","alex","egon","lxx"]
linuxs = ["lili","hanmeimei","張三","egon","lxx","jay"]
l=[]
for name in pythons:
if name in linuxs:
l.append(name)
print(l)>>>>>['egon', 'lxx']
集合型別set基本使用
1、用途:
去重
(1) 無法保證順序
msg = "hello" res=set(msg)>>>>{'0','l','e','h'} 無順序 print(''.join(res))>>>>oleh names = ['egon','lxx','lili',"egon","egon"] print(list(set(names)))>>>>>>['egon', 'lxx', 'lili'] 去重
(2)只能針對不可變元素的去重
students_info = [ {"name":"egon","age":18,"gender":"male"}, {"name":"tom","age":19,"gender":"male"}, {"name":"jack","age":38,"gender":"female"}, {"name":"egon","age":18,"gender":"male"}, {"name":"egon","age":18,"gender":"male"}, ] new_l = [] for info in students_info: if info not in new_l: new_l.append(info) print(new_l)>>>>>[{'name': 'egon', 'age': 18, 'gender': 'male'}, {'name': 'tom', 'age': 19, 'gender': 'male'}, {'name': 'jack', 'age': 38, 'gender': 'female'}]
關係運算
2、定義方式: 在{}內用逗號分隔開多個元素,集合內元素的特點有三個
(1)集合內元素必須是不可變型別
(2)集合內元素不能重複
(3)集合內元素無序
s = {11,3.1,"xxx",(1,2,3),}
s = {11,11,11,11,11,22,33} # s = set(...)
print(s)
print(type(s))
資料型別轉換
res = set("hello")>>>>>字串轉集合
print(res)
s = set()
print(s,type(s))
3、常用操作+內建的方法
pythons = {"tom","jack","alex","egon","lxx"}
linuxs = {"lili","hanmeimei","張三","egon","lxx","jay"}
(1)交集:取兩個集合的共同部分->既報名pythons又報名linuxs的學生
print(pythons & linuxs)
print(pythons.intersection(linuxs))
pythons = pythons & linuxs
pythons.intersection_update(linuxs)
(2)並集:兩個集合併到一起->所有學生的姓名
print(pythons | linuxs)
print(pythons.union(linuxs))
(3)差集: 一個集合減掉與另外一個集合共同的部分
只學了python的學生姓名
print(pythons - linuxs)
print(pythons.difference(linuxs))
只學了linux的學生姓名
print(linuxs - pythons)
(4) 交叉補集/對稱差集:兩個集合互相減,然後再併到一起-》取沒有同時學兩門課程的學生
res = (pythons - linuxs) | (linuxs - pythons)
res = pythons ^ linuxs
print(res)
print(pythons.symmetric_difference(linuxs))
(5)父子集合:當一個集合完全包含了另外一個集合,該集合才能稱爹
s1 = {1,2,3}
s2 = {3,4,5}
print(s1 >= s2)
print(s2 <= s1)
s1 = {1,2,3}
s2 = {1,2}
print(s1 >= s2)
print(s1.issuperset(s2))
print(s2 <= s1)
print(s2.issubset(s1))
需要掌握的
s1 = {1,2,3}
1、s1.update()
s1.update({3,4,5})
print(s1)
2、s1.add()
s1.add(4)
print(s1)
3、刪除
s1 = {11,22,33,44,55,"xx","yy","zz","aa"}
s1.remove(3)
print(s1)
s1.remove(333333333)
s1.discard(333333333)
print(s1)
res=s1.pop()
print(s1)
print(res)
s1.clear()
print(s1)
s1 = {11,22,33,44,55,"xx","yy","zz","aa"}
s1.copy()
4、s1.isdisjoint()判斷是否是無交集
s1 = {1,2,3}
s2 = {3,4,5,6}
print(s1.isdisjoint(s2))
==該型別總結
存多個值
無序
可變
s1 = {1,2,3}
print(id(s1))
s1.add(4)
print(id(s1)) 不變
==檔案處理(1)
致命三連擊!!!
1、什麼是檔案
檔案是作業系統提供給使用者或者應用程式操作硬碟的一種機制
2、為何要用檔案
讀寫檔案----->存取硬碟
應用程式: open()
作業系統: 開啟檔案
計算機硬體: 硬碟空間
3、如何用檔案
開啟檔案
讀/寫
關閉檔案
f = open
f = open(r"a\a.txt",mode="rt",)
f的值-》檔案控制代碼,檔案物件
res = f.read()
print(res,type(res))
f.close() # 回收作業系統的資源
print(f)
f.read()
with 上下文管理,子程式碼執行完畢可自動回收作業系統資源
with open(r"a\a.txt",mode="rt",) as f,
open(r"a\b.txt",mode="rt",) as f1:
res = f.read()
with open(r"a.txt",mode="rt",) as f:
for line in f:
# print(line)
res=line.strip('\n').split('