python seek()

1、seek函数 

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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、示例

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 a tape."

rewind(current_file)

print "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)

$ python ex20.py test.txt
First let's print the whole file:

To all the people out there.
I say I don't like my hair.
I need to shave it off.

Now let's rewind, kind of like a tape.
Let's print three lines:
1 To all the people out there.

2 I say I don't like my hair.

3 I need to shave it off.

$