python3文件操作

文件操作的过程

1）打开

2）操作

3）关闭

1.写(清空写入)

# f = open(file='test', mode='w', encoding='utf-8')　　# 第一种情况
# f.write("Hello World!")
# f.close()

# f = open(file='test', mode='wb')　　# 第二种情况　　　　　　
# f.write("杨".encode('utf-8'))
# f.close()

# with open(file='test', mode='w', encoding='utf-8') as  f:　　# 第三种情况
#     f.write("高圆")

with open(file='test', mode='wb') as f1:　　# 第四种情况
    f1.write("李璐".encode('utf-8'))

2.读

# 读
# f = open(file='test', mode='r', encoding='utf-8')
# data = f.read()
# print(data)
# f.close()

# f = open(file='test', mode='rb')
# data = f.read()
# print(data.decode('utf-8'))
# f.close()

# with open(file='test', mode='r', encoding='utf-8') as f1:
#     data = f1.read()
#     print(data)

with open(file='test', mode='rb') as f1:
    data = f1.read().decode('utf-8')
    print(data)

3.追加写入

# 追加
# f = open(file='test', mode='a', encoding='utf-8')
# f.write('\nWhat?')
# f.close()

# f = open(file='test', mode='ab')
# f.write("\ntom".encode('utf-8'))
# f.close()

# with open(file='test', mode='a', encoding='utf-8') as f1:
#     f1.write("\nHi")

with open(file='test', mode='ab') as f1:
    f1.write('\njoker'.encode('utf-8'))

4.读写

# 读写

# f = open(file='test', mode='r+', encoding='utf-8')
# data = f.read()
# print(data)
# f.write("\tok")
# f.close()

# f = open(file='test', mode='r+b')
# data = f.read().decode('utf-8')
# print(data)
# f.write('\tfun'.encode('utf-8'))
# f.close()

# with open(file='test', mode='r+', encoding='utf-8') as f1:
#     data = f1.read()
#     print(data)
#     f1.write("\tfine")

with open(file='test', mode='r+b') as f1:
    data = f1.read().decode('utf-8')
    print(data)
    f1.write('\tsad'.encode('utf-8'))

5.清空写读

# 清空写读

# f = open(file='test', mode='w+', encoding='utf-8')
# f.write("blue")
# f.seek(0)
# data = f.read()
# print(data)

# f = open(file='test', mode='w+b')
# f.write("joker".encode('utf-8'))
# f.seek(0)
# data = f.read().decode('utf-8')
# print(data)

# with open(file='test', mode='w+', encoding='utf-8') as f1:
#     f1.write("Hello World!")
#     f1.seek(0)
#     data = f1.read()
#     print(data)

with open(file='test', mode='w+b') as f1:
    f1.write("Thank you!".encode('utf-8'))
    f1.seek(0)
    data = f1.read().decode('utf-8')
    print(data)

6.追加写读

# 追加写

# f = open(file='test', mode='a+', encoding='utf-8')
# f.write("\ttom")
# f.seek(0)
# data = f.read()
# print(data)

# f = open(file='test', mode='a+b')
# f.write("\ttom".encode('utf-8'))
# f.seek(0)
# data = f.read().decode('utf-8')
# print(data)

# with open(file='test', mode='a+', encoding='utf-8') as f1:
#     f1.write("\tjoker")
#     f1.seek(0)
#     data = f1.read()
#     print(data)

with open(file='test', mode='a+b') as f1:
    f1.write("\ttom".encode('utf-8'))
    f1.seek(0)
    data = f1.read().decode('utf-8')
    print(data)

7.常用方法

1）read(n)

光标位置m，读取从m->m+n，n个字符

2）seek(n)

设置光标的位置，n为字节（从0开始）

3）tell()

获取当前光标的位置，单位是字节

with open(file='test1', mode='r+', encoding='utf-8') as f:
    f.seek(3)       # 设置光标位置，字节
    data = f.read(2)    # 读取，字符
    a = f.tell()    # 获取光标位置，字节
    print(data, '\t', a)

4）按行读取

a.for循环

with open(file='test1', mode='r+', encoding='utf-8') as f:
    for line in f:
        print(line)

b.readlines

readlines()，打印的是list，一行作为一个元素

with open(file='test1', mode='r+', encoding='utf-8') as f:
    data = f.readlines()
    print(data)

c.readline()

读取一行

with open(file='test1', mode='r+', encoding='utf-8') as f:
    data = f.readline()
    print(data)

d.truncate(n)

n为空时，从当前位置截断

n不为空时，从n开始截断（n后的内容舍弃）

n为字节

with open(file='test', mode='w', encoding='utf-8') as f:
    f.write("你好，之华，之南")
    f.truncate(6)