笨办法学习python3练习代码ex20.py 函数和文件

 1 #函数和文件
 2 #readline：只读取文本文件的一行
 3 #seek(0):将读写位置移动到文件开头
 4 from sys import argv
 5 script , input_file = argv      # input_file = ex20.txt
 6                                 #ex20.txt 至少有三行数据


 7 def print_all(f):               # f 为文件名
 8     print(f.read())             #读取完文件后，指针指向文件末尾
 9     
10 def rewind(f):
11     f.seek(0)                   #seek(0):将读写位置移动到文件开头
12     
13     
14 #readline：只读取文本文件的一行 ，下次读取自动接着下一行开始读取  
15 def print_a_line(line_count, f):
16     print(line_count, f.readline())
17     
18 current_file = open(input_file)
19 
20 print("First let‘s print the whole file: \n")
21 print_all(current_file)
22 print("Now let‘s rewind, kind of like a tape.")
23 rewind(current_file)
24 
25 print("Let‘s print three lines:")
26 current_line = 1
27 print_a_line(current_line, current_file)
28 
29 current_line = current_line + 1
30 print_a_line(current_line, current_file)
31 
32 current_line = current_line + 1
33 print_a_line(current_line, current_file)
34