Question

def file_open(filename):
    fo=open(filename,'r')
    #fo.seek(5)
    fo.read(3)
    fo.close()

file_open("file_ro.py")

I expect above program to return first 3 bytes from file . But it returns nothing. When I ran these in interactive python command prompt – I get expected output!

Answer 1

While your own answer prints the bytes read, it doesn’t return them, so you won’t be able to use the result somewhere else. Also, there’s room for a few other improvements:

• file_open isn’t a good name for the function, since it reads and returns bytes from a file rather than just opening it.
• You should make sure that you close the file even if fo.read(3) fails. You can use the with statement to solve this issue.

The modified code could look something like this:

def read_first_bytes(filename):
    with open(filename,'r') as f:
        return f.read(3)

Usage:

>>> print read_first_bytes("file.py")