[Tutor] Created Function, Need Argument to be a String

[Matt Williams]

Use the str() function.

M

On Thu, 15 Dec 2016, 07:56 Bryon Adams, <bryonadams at openmailbox.org> wrote:

> Is there a way to force my argument to always be a string before
> entering the function? Else, is there a better way to go about this? In
> whatever program I write, I could change what I want as input to be a
> string prior to tossing it into the function but I think it would make
> more sense for my function to already do it. The function otherwise
> works. This is on Python3.5 under Fedora 25
>
> The only other thing I could think of would be to put exceptions in for
> syntax error and whatever else pops up as I go along, though to be
> honest it *should* always be a string that gets dumped into the
> function. Not sure how I'd put the exception together though since it's
> not making it into the function prior to failing.
>
> -------------------------------------------
> Error from interpreter: (looks like it's taking issue with it being a
> number it doesn't know how to deal with)
>
>  >>> ip_checker(169.254.0.1)
>    File "<stdin>", line 1
>      ip_checker(169.254.0.1)
>                         ^
> SyntaxError: invalid syntax
>
> -------------------------------------------
> My function:
>
> def ip_checker(ip_address):
>    '''
>    Takes one IP address and checks whether it is valid or not.
>    '''
>    # Try to convert to integers
>    try:
>      ip_addr = [int(i) for i in ip_address.split('.')]
>    except ValueError:
>      print('Invalid characters were entered or an octet is empty, please
> try again.')
>      return False
>
>    # Determine how many octets were entered
>    if len(ip_addr) != 4:
>      print('Incorrect number of octets, please try again.')
>      return False
>
>    # Determine validity of first octet
>    if ((ip_addr[0] > 223) and (ip_addr[0] < 256)) or (ip_addr[0] == 0):
>      print('First octet is reserved or zero.')
>      return False
>
>    # Determine if this is a loopback address
>    if ip_addr[0] == 127:
>      print('I think that was a loopback address, please try again.')
>      return False
>
>    # Determine if this is an APIPA address
>    if (ip_addr[0] == 169) and (ip_addr[1] == 254):
>      print('I think that was an APIPA address, please try again.')
>      return False
>
>    # Determine if the last three octets are between 0-255
>    for octet in (ip_addr[1], ip_addr[2], ip_addr[3]):
>      if octet not in [i for i in range(0,256)]:
>        print('Octet too large or too small, please try again.')
>        return False
>      else:
>        print('The IP address {} is valid.'.format(ip_address))
>        return True
>
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