重拾python 二十

將函數與文件操作結合起來使用，見ex20.py：

#!/usr/bin/python                                                                                                
# -*- coding: utf-8 -*-

from sys import argv

script, input_file = argv

def print_whole_file(f):
    print f.read()

def reset_file_flag(f):
    f.seek(0)

def print_one_line(line_count, f): 
    print line_count, f.readline()

current_file = open(input_file)

print "First let's print the whole file:"

print_whole_file(current_file)

print "Now let's reset_file_flag, kind of like a tape."

reset_file_flag(current_file)

print "Let's print three lines:"

current_line = 1 
print_one_line(current_line, current_file)

current_line = current_line + 1 
print_one_line(current_line, current_file)

current_line = current_line + 1 
print_one_line(current_line, current_file)

運行：

python ex20.py ex20_op.py

得到：

First let's print the whole file:
line1
line 2
line three
line forth
line 5th

Now let's reset_file_flag, kind of like a tape.
Let's print three lines:
1 line1

2 line 2

3 line three