代码串

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)

结果

PS C:\Users\HH\lpthw> python ex12.py test.txt
First let's print the whole file:


Now let's rewind, kind of like a tape.
let's print three lines:
1
2
3
PS C:\Users\HH\lpthw>

PS C:\Users\HH\lpthw> python ex12.py test.txt
First let's print the whole file:


Now let's rewind, kind of like a tape.
let's print three lines:
1
2
3
PS C:\Users\HH\lpthw>