decimal->binary python script... yes, I suck at programmi

[Monkeywrench]

sorry if this is not the forum for these sorts of questions..
Python's my first language, I started learning it before the summer of this year, but never really got into it. Anyway, I'm trying to pick it up.. I wrote a silly little program to convert decimal values to binary. I'd just like suggestions on what could be done in a better, more efficient way. Thanks

Code: Select all

#!/usr/bin/python

def convert(decvalue):
        """This will convert the decimal input value to binary and return it"""
        print decvalue,"is the decimal value to convert"
        binnum=""
        while decvalue != 0:
                remain=decvalue%2
                decvalue=decvalue/2
                if remain == 1:
                        binnum = "1" + binnum
                else:
                        binnum = "0" + binnum
        return binnum    

deci=input("Give me the decimal value: ")
print convert(deci)

Sample output:

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Give me the decimal value: 21
21 is the decimal value to convert
10101

And another thing.. before, I had the line binnum="" outside of the function (in other words, I put the line right after the deci=input... line) but I got an error:

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UnboundLocalError: local variable 'binnum' referenced before assignment

Erm, what's this mean?

[_dook_master_]

sorry if this is not the forum for these sorts of questions..
Python's my first language, I started learning it before the summer of this year, but never really got into it. Anyway, I'm trying to pick it up.. I wrote a silly little program to convert decimal values to binary. I'd just like suggestions on what could be done in a better, more efficient way. Thanks

Code: Select all

#!/usr/bin/python

def convert(decvalue):
        """This will convert the decimal input value to binary and return it"""
        print decvalue,"is the decimal value to convert"
        binnum=""
        while decvalue != 0:
                remain=decvalue%2
                decvalue=decvalue/2
                if remain == 1:
                        binnum = "1" + binnum
                else:
                        binnum = "0" + binnum
        return binnum    

deci=input("Give me the decimal value: ")
print convert(deci)

Sample output:

Code: Select all

Give me the decimal value: 21
21 is the decimal value to convert
10101

And another thing.. before, I had the line binnum="" outside of the function (in other words, I put the line right after the deci=input... line) but I got an error:

Code: Select all

UnboundLocalError: local variable 'binnum' referenced before assignment

Erm, what's this mean?

I'm not sure how Python handles things, as I don't write in it, but from common logic I'd assume that since you label binnum="", that it thinks it is a string.

[SZwarts]

• * Your "if" statement is redundant
  * You can use operator= assignemnts like += /= that doesn't make anything more or less efficient, just easier to read
  * You can do without the variable remain

Code: Select all

UnboundLocalError: local variable 'binnum' referenced before assignment

Erm, what's this mean?

It means that you're using a read out before an assigment. It's in the line
binnum= "1"+binnum. Since you don't declare type in python explicitely python has no idea what binnum is. So it first tries to calculate "1"+binnum and then tries to assign it to binnum. But because the type of binnum is unknown it does not no if it can actually "add" binnum to the string "1" (maybe it's not a string but an integer and how can you add an integer to a string?), hence you're not allowed to use variables in python before you have assigned them.
So see the binum="" as a type declaration
Well hope that was clear enough...

Code: Select all

def convert(decvalue):
  print decvalue,"is the decimal value to convert"
  binnum=""
  while decvalue !=0:
    binnum=str(decvalue%2)+binnum
    decvalue/=2
  return binnum

deci=input("Give me the decimal value: ")
print convert(deci)

[Monkeywrench]

Thanks for the input

SZ: wow.. your version is quite a bit shorter.. heh could you explain this line: "decvalue/=2" does it just mean "set decvalue equal to decvalue/2"?

Thanks again

[SZwarts]

SZ: wow.. your version is quite a bit shorter.. heh could you explain this line: "decvalue/=2" does it just mean "set decvalue equal to decvalue/2"?

Yes.

Example:

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i=0
i+=1 #i=1
i+=3 #i=4
i*=3 #i=12
i/=4 #i=3

teststring="test"
teststring+="ing" #teststring="testing"