Python文件读写open函数详解

filename = 'test.txt'
# 以只读方式打开test.txt文件
fd = open(filename, 'r', encoding='utf-8')
# fd.read(self, n) 按指定的长度读取文件内容,为空则读取全部内容
lines = fd.read()
print(lines)
fd.close()
print('------------------read------------------------')

# 以写入模式打开test.txt文件
fd = open(filename, 'w', encoding='utf-8')
# fd.write(self, str) 将str写入文件
lines_w = fd.write('java\nPython\tGolang')
print(lines_w)
fd.close()
print('------------------write------------------------')

# 以追加模式打开文件
fd = open(filename, 'a', encoding='utf-8')
lines_a = fd.write('java\nPython\tGolang')
print(lines_a)
fd.close()
print('------------------append------------------------')

# 以读写模式打开文件(r+)
fd = open(filename, 'r+', encoding='utf-8')
print(fd.read())
lines_str = fd.write('java\nPython\tGolang')
print(fd.read())
fd.close()
print('------------------readWrite------------------------')

# 以读写模式打开文件(w+)
fd = open(filename, 'w+', encoding='utf-8')
lines_str = fd.write('java\nPython\tGolang')
print(fd.read())        # 文件打开时清空文件内容，虽然写入了文件，但未保存，因此读取文件为空
fd.close()
print('------------------readWrite------------------------')

# 以读写模式打开文件(a+)
fd = open(filename, 'a+', encoding='utf-8')
print(fd.read())
# 按行读取
print(fd.readlines(2))
lines_str = fd.write('java\nPython\tGolang')
print(fd.read())
fd.close()
print('------------------readWrite------------------------')