我在犯什么错误？

Question

我正在学Python从了解Python的艰难之路。这是给出的练习之一，但是我的输出结果与应该看到的内容部分不符。 Here is the output snap. The 2nd line is printed in number 3 and the 3rd line isn't printed at all.

这里是我的代码：

from sys import argv 

script, input_file = argv 

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 tape." 

rewind(current_file) 

print "Let's print three lines: " 

current_line = 1 
print_a_line(current_line, current_file) 

current_line += 1 
print_a_line(current_line, current_file) 

current_line += 1 
print_a_line(current_line, current_file) 

是有一些问题，在我的系统readline()？这不是第一次发生这种情况。

Answer 1

您的test.txt文件包含多个空白行。你必须删除它们，特别是在line1和line2之间。它会解决你的问题。

不空行：

First let's print the whole file: 

this is line1.Say hello. 
this is line2. This must be printed!! 
this is line3.This is cool!Print please 

now let's rewind, kind of like tape. 
Let's print three lines: 
1 this is line1.Say hello. 

2 this is line2. This must be printed!! 

3 this is line3.This is cool!Print please 

在你的情况（空行），您只需打印的空行开始与“2”（这意味着全局变量current_line有效增加）：

First let's print the whole file: 

this is line1.Say hello. 

this is line2. This must be printed!! 

this is line3.This is cool!Print please 

now let's rewind, kind of like tape. 
Let's print three lines: 
1 this is line1.Say hello. 

2 

3 this is line2. This must be printed!!