[Tutor] python string __add__

[Alan Gauld]

> I have a script that will take decimal numbers of any length as
command
> line arguments and output the binary equivalent.

Its probably easier to just use the mathematical algorithm for
converting numbers using repeated modulo division, however....

> spaces.  Is there a way for python string __add__ to output 
> binary digits with no spaces ?

> """ a program that takes decimal numbers of any length as
> space-delimited command line arguments and outputs binary 
> numbers separated by newline"""

I take that to mean:

foo 123456 234 98765433456789007 4

[----
 Or do you mean:

foo 1 2 3 4 5 6 7 8 9 6 7 8 3 4 7 2 1 4

I'm not sure... An example is ghood in a doc string...
---]

> dict = {
>            '0' : '0000',
>            '1' : '0001',
etc
>            '9' : '1001'
>        }

BTW You have just lost the ability to convert to a dict type 
by stealing the name as a variable... probably a bad idea!


> length = len(sys.argv[1:])
> while length > 0:
>     for i in range(length):
>         w = sys.argv[-length]
>         length = length - 1

That's a complicated way of stepping through each number 
in the command string.

for w in sys.argv[1:]:

>         list1 = list(w)
>         list1.reverse()
>         length2 = len(list1)
>         while length2 > 0:
>             for i in range(length2):
>                 w = list1[length2 - 1]  # w = list1[-1]??
>                 length2 = length2 - 1

I *think" this just reads the characters (digits) in reverse order. 
But since you already reversed the list why not miss all the hassle 
and just read them in normal order:

       for i in w:

> #                x.__add__(dict[w])

You should never call a python operator function like that. 
You probably should do something like:

x = x + dict[w]

>                 x = dict[w]

This will convert your numbers into binary coded decimal not true 
binary. ie you are simply converting each digit into its binary 
equivalent and concatenating them.

eg

decimal      BCD         binary
8            1000        1000        OK so far
15           00010101    1111        Oops!

None of that actually answers your question about string 
concatenation!

Try:

s = "%s%s" % (string1,string2)
OR
s = string1 + string2

s will contain the two strings joined together with no spaces.

HTH,

Alan G
Author of the Learn to Program web tutor
http://www.freenetpages.co.uk/hp/alan.gauld