python入门_老男孩_文件操作

写

　　只写　

# 只写
# utf-8
f = open('us', mode='w', encoding='utf-8')
f.write('tonight, i can write down the most beautiful lines')
f.close

# bytes
f = open('us', mode='wb') 
f.write('如果可以'.encode('utf-8'))
f.close()

　　

　　写读

# 读写
f = open('us', mode='w+', encoding='utf-8')
f.write('信念和勇气')
print(f.read()) # 空白
f.close()

 　　　　光标定位

# 读写
f = open('us', mode='r+', encoding='utf-8')
f.write('信念和勇气')
f.seek(0)
print(f.read())
f.close()

　　

读

　　只读

# 只读
f = open('us', mode='r', encoding='utf-8')
content = f.read()
print(content)
f.close()

f = open('us', mode='rb') # 以bytes方式,方便传输
content = f.read()
print(content, type(content))
f.close()

　　　　按照字符开始读

# 读写
f = open('us', mode='r+', encoding='utf-8')
f.write('信念和勇气')
print(f.read(3))
f.close()

　　　　按照字节定光标 / 前往后

# 读写
f = open('us', mode='r+', encoding='utf-8')
f.write('新年贺卡')
f.seek(3)
print(f.read())
f.close()

　　　　定光标 +  读 / 后往前

# 定光标，读特定数目字符
f = open('us', mode='r+', encoding='utf-8')
f.write('新年贺卡恭喜发财')
count = f.tell()
f.seek(count-9)
print(f.read(1))
f.close()

　　读写

# 读写
f = open('us', mode='r+', encoding='utf-8')
print(f.read())
f.write('信念和勇气')
f.close()

　　

追加

# 追加
f = open('us', mode='a', encoding='utf-8')
f.write('ZHAO')
f.close()

f = open('us', mode='ab')
f.write('ZHAO'.encode('utf-8'))
f.close()

推荐读写方式　

with open('us', mode='r+', encoding='utf-8') as obj:
    obj.read()
    print(obj)

# 打开多个文件
with open('us', mode='r+', encoding='utf-8') as obj, open('us', mode='r+', encoding='utf-8') as obj1:
    obj.read()
    obj1.write('hello,world')
    print(obj)

用文件读写的方式登陆用户

# 文件读写方式登陆用户,三次机会
username = 'xiaozhao'
password = '20181009'

with open('us', mode='w', encoding='utf-8') as f:
    f.write('{}
{}'.format(username,password))

    
i = 0
lis = []
while i < 3:
    usr = input('请输入用户名：')
    pwd = input('请输入密码：')

    with open('us', mode='r', encoding='utf-8') as f:
        for k in f:
            lis.append(k)
    
    if usr == lis[0].strip() and pwd == lis[1].strip():
        print('登陆成功')
        break
    else:
        print('登陆失败')