笨办法学Python：函数和文件

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:
"
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)

常见问题之Q2: 文件中为什么有3个空行？

函数 readline() 返回一行以 结尾的文件内容， 在你调用print函数的最后增加一个逗号','，用来避免为每一行添加两个换行符

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