python3中name'current_line'未定义

learn python the hard way中习题20\n
运行时在cmd中以下这段代码报错：
print_a_line(current_line,current_file)
NameError: name 'current_line' is not defined_
我用查找前后变量名也是一致的。。不知道未定义是什么情况

print("Let's print three lines :")

#读取各行
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)

以下是完整的代码片段

 from sys import argv

script,input_file = argv

#输出文本内容
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 :")

#读取各行
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)

你代码的第一行多了一个空格，不知道是不是复制代码时造成的，但是我把空格去掉在我的电脑上运行你的代码是可以正确输出的

我试了一下，没有问题，原来我的测试文件中带了中文，后面加了utf-8的编码后就可以了

 from sys import argv

script,input_file = argv
print(script,input_file)

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,encoding='utf-8')

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 :")

#读取各行
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)