python 3 the hard way lesson 20

#exe 20
#run it with something like this
#C:\Python33>python PTHW20.py 1.txt.txt
#
#
#read the errors! Typos can block you!

from sys import argv

#the script at the front is required but it's not a key word
script, input_file=argv

def print_all(f):
    f.seek(0) #to change the file object’s position, use f.seek(offset, from_what)

#the function is called below to iterate the lines one by one
def print_a_line(line_count,f):
    print (line_count, f.readline())

def rewind(f):
    f.seek(0)

#open the file that was called with input_file arg
#eg
#C:\Python33>python PTHW20.py 1.txt.txt
current_file = open(input_file)
print ("Here's the file name you wanted to open {}".format(input_file))

print()
print ("First, let's print the contents of the whole file:\n")

print(current_file.read())
print_all(current_file) #didn't work
print()
print ("Now, let's rewind kind of like a tape.")

# calls the above function
rewind(current_file)

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

current_line = 1 #the interation worked but not current_file
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)