1、seek函数
file.seek(off, whence=0)：从文件中移动off个操作标记（文件指针），正往结束方向移动，负往开始方向移动。如果设定了whence参数，就以whence设定的起始位为准，0代表从头开始，1代表当前位置，2代表文件最末尾位置。
2.例子
#!/usr/bin/env python3 from sys import argv #arg[0] is seek.py, argv[1] is the input_file input_file = argv[1] def print_all(f): print(f.read()) def rewind(f): f.seek(0) def print_a_line(line_count,f): print(line_count,f.readline()) current_file = open(input_file) print("First let's print the whole file:\n") print_all(current_file) print("Now let's rewind,kind of like a tape.") rewind(current_file) print("Now let's print three lines.") current_line = 1 print_a_line(current_line,current_file) current_line = current_line + 1 print_a_line(current_line,current_file) current_line = current_line + 1 print_a_line(current_line,current_file)
