Zed Shaw 练习 20 不起作用[关闭]

Question

当我在下面输入时：

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)

它不能在我的 powershell 中打印或工作它应该打印这个：

First let’s print the whole file:
This is line 1
This is line 2
This is line 3
Now let’s rewind, kind of like a tape.
Let’s print three lines:
1 This is line 1
2 This is line 2
3 This is line 3

在 powershell 中输入：$ python ex20.py test.txt

Answer 1

你没有打电话。您的脚本定义了函数，但从未实际使用任何函数。

这是因为所有应该调用函数的行都缩进为print_a_line() 函数的一部分。取消缩进将它们移动到模块级别，以便在脚本运行时执行它们：

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)