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A program of changing the base!

Many times when you wish to bash a problem with 'programming-bash', changing base of a number is needed. Of course we can use wolfram, but it'll get irritating if there are too many numbers.

So here, \(\color{Blue}{\text{Python comes to our help!}}\)

I've written this program in Python 2.7, for getting a decimal number in some other base...

(\(\text{cb}\) stands for change_base )

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from math import log
def cb(n,m):
    """Returns decimal integer n in base m"""
    if m<1 or m>36 or int(m)!=m:
        return 0
    if m==1:
        return '1'*n
    k=''
    y=int(log(n,m))
    while not y<0:
        p=n/m**y
        if p<10:
            k+=str(p)
        if p>=10:
            letters=['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z']
            k+=letters[p-10]
        n=n-p*m**y
        y-=1
    return k

  • This works for bases 1 to 36.

First I had written that using the while loop for \(n\), got pretty bad... It left zeroes that come in between, and also I couldn't efficiently assign Alphabets to digits greater than 9.

But now, I've made it shorter and efficient with the while loop for \(y\).


Here's the program for the other way, changing a number from other way, into decimal!

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def basedecode(string,m):
    """Input string in base m, outpt decimal equivalent!"""
    k=list(string.upper())
    p=['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z']
    while any(i in k for i in p) is True:
        for i in p:
            if i in k:
                k[k.index(i)]=str(p.index(i)+10)
    u=0
    for i in xrange(len(k)):
        u+=int(k[i])*m**(len(k)-i-1)
    return u

I want to know if there are any improvements that you can spot, thanks!

Note by Aditya Raut
2 years, 5 months ago

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1 vote

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@Aditya Raut Can you please give me some further sources than Codecademy. I guess you also learnt from there at first. But I want to know if there is any "advanced" source like CA. The course at CA is quite limited.

Kartik Sharma - 2 years, 5 months ago

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I didn't learn from codeacademy, I learnt from 1-2 books and mainly, experimenting...

Aditya Raut - 2 years, 5 months ago

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@Aditya Raut r u a bio student or a cs student. u once posted about a cockroach.

Aditya Kumar - 2 years, 5 months ago

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@Aditya Kumar Well thats now worth a LOL, I am neither bio student nor cs student! officially , I've taken 'Electronics' as a subject for my 12th std board exam...

Aditya Raut - 2 years, 5 months ago

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@Aditya Raut Amazing! Y aren't u posting questions these days?

Aditya Kumar - 2 years, 5 months ago

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@Aditya Raut By the way, I am a 'bio student' in terms of pen and paper but that does not mean I am not a computer science student by heart.

Agnishom Chattopadhyay - 2 years, 4 months ago

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That is great. Experimenting is the best way to learn. Especially in programming. I learn programming the same way.

Agnishom Chattopadhyay - 2 years, 4 months ago

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The standard way to convert a string in base \(b\) to an integer is int(string,b),by the way

Agnishom Chattopadhyay - 2 years, 4 months ago

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What is just happening!

So all I did was nothing but an \(\text{exercise}\) of no real use, just use int(str,b)..... Why does this keep happening with me!

Thank you btw, for telling this amazing shortcut, where'd you learn that?

Aditya Raut - 2 years, 4 months ago

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I don't exactly remember but I guess stackoverflow.

Agnishom Chattopadhyay - 2 years, 4 months ago

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There is a typo in cb(n,m) line 7. It should be return '1'*n

Pranjal Jain - 2 years, 5 months ago

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Aditya, what's' your rank in JEE advanced?
Why don't you check your mail.

Shivam Jadhav - 2 years, 5 months ago

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he's in 12th now

Aditya Kumar - 2 years, 5 months ago

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