预科班D11
2024-09-07 17:41:27
2020.09.21星期一 预科班D11
学习内容:
一、基本数据类型及内置方法
1、整形int及浮点型float
+ - * / // ** % > < >= <=
2、字符串类型
(1)按索引值(正向取+反向取):只能取
name = "jack"
print(name[0]) # j
print(name[-1]) # k
name[0] = "A" # 报错
(2)切片(顾头不顾尾)
msg = "hello world"
print(msg[2:5]) # llo
print(msg[2]+msg[3]+msg[6]) # llw
(3)长度len
msg = "hello world"
print(len(msg)) # 11
(4)成员运算in和not in
msg = "hello world"
print("heo" in msg) # False
print("hel" not in msg) # False
(5)移除空白strip
msg = " hello "
res = msg.strip()
print(len(res)) # 5
# 练习
inp_usr = input("username>>>:").strip()
inp_pwd = input("password>>>:").strip()
if inp_usr == "jack" and inp_pwd == "123":
print("登陆成功!")
else:
print("登陆失败!")
(6)切分spilt
info = "root:x:0:0::/root:/bin/bash"
res = info.spilt(':')
print(res[-2]) # /root
(7)循环
msg = "hello"
for x in msg:
print(x)
#h
#e
#l
#l
#o
3、列表类型
l = ['a', 1111, 'c']
l[0] = 'A'
print(l) # A 1111 c
(1)按索引存取值(正向存取+反向存取):既可存也可取
l = ['a', 1111, 'c']
l[3] = 666
print(l) # a 1111 c 666
(2)切片(顾头不顾尾,步长)
l = [111, 222, 333, 444, 555]
print(l[0:3]) # 111 222 333
(3)长度
l = ['a', 1111, 'c']
print(len(l)) # 3
(4)成员运算in和not in
l = ['a', 1111, 'c']
print('c' in l) # True
print(1111 in l) # True
(5)追加
l = ['a', 1111, 'c']
l.append('d')
l.append('d')
print(l) # a 1111 c d d
l = ['a', 1111, 'c']
l.insert(1,6666)
print(l) # a 6666 111 c
(6)删除
l = [111, 222, 333, 444, 555]
del l(2)
print(l) # 111 222 444 555
(7)循环
l = [111, 222, 333, 444, 555]
for x in l:
print(x)
4、字典型dict
(1)按key存取值:可存可取
dic={"k1":111, "k2":2222}
dic["k1"] = 666
print(dic) # {"k1":666, "k2":2222}
dic={"k1":111, "k2":2222}
dic["k3"] = 7777
print(dic) # {"k1":111, "k2":2222, "k3":7777}
(2)长度
dic={"k1":111, "k2":2222}
print(len(dic)) # 2
(3)成员运算in和not in
dic={"k1":111, "k2":2222}
print("k1" in dic) # True
print(2222 in dic) # False
(4)删除
dic={"k1": 111, "k2": 2222}
del dic["k1"]
print(dic) # {"k2": 2222}
(5)循环
dic={"k1":111, "k2":2222}
for x in dic:
print(x, dic(x))
二、文件处理
文本编辑
name = input("请输入你的用户名:")
f = open("user.txt", mode='w')
# print(f)
f.write(name)
f.close()
f = open("user.txt", mode='w')
# print(f)
f.write("hello")
f.close()
f.write("world") # world报错,因为文件已关闭
文本查看
f = open("user.txt",mode='r')
data = f.read()
print(data)
f.close() # 一次性读取,对内存要求高,速度快
f = open("user.txt",mode='r')
for line in f:
print(line,end="")
f.close() # 按行读取,对硬盘要求高,速度略慢
文件的修改
f = open("user.txt", mode='r+')
f.seek(6)
f.write("wo")
f.close() # 你好hello 改为 你好wollo
#先以读的形式将user.txt全部读入内存,在内存中修改文件内容且保存在内存中
f = open("user.txt",mode='r', encoding='utf-8')
data = f.read()
res = data.replace("你好","666")
print(res)
f.close()
#以写的形式打开文件,将文件中内容清除掉(原文件内存中有备份)
f = open("user.txt", mode='w',encoding='utf-8')
#将新内容覆盖原文件
f.write(res)
f.close()
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