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Groups > comp.lang.python > #55303 > unrolled thread

Efficency help for a Calculator Program

Started byJonDoe297 <vignesh.harikrishna@gmail.com>
First post2013-10-02 03:44 -0700
Last post2013-10-04 16:45 +1000
Articles 7 — 3 participants

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  Efficency help for a Calculator Program JonDoe297 <vignesh.harikrishna@gmail.com> - 2013-10-02 03:44 -0700
    Re: Efficency help for a Calculator Program Chris Angelico <rosuav@gmail.com> - 2013-10-02 21:01 +1000
      Re: Efficency help for a Calculator Program JonDoe297 <vignesh.harikrishna@gmail.com> - 2013-10-02 06:43 -0700
    Re: Efficency help for a Calculator Program Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-10-02 19:47 -0400
    Re: Efficency help for a Calculator Program Chris Angelico <rosuav@gmail.com> - 2013-10-03 10:25 +1000
    Re: Efficency help for a Calculator Program Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-10-03 19:15 -0400
    Re: Efficency help for a Calculator Program Chris Angelico <rosuav@gmail.com> - 2013-10-04 16:45 +1000

#55303 — Efficency help for a Calculator Program

FromJonDoe297 <vignesh.harikrishna@gmail.com>
Date2013-10-02 03:44 -0700
SubjectEfficency help for a Calculator Program
Message-ID<77bde84a-b0ce-4061-bb2e-e6cd23f4282c@googlegroups.com>
You may remember me from this : 

https://groups.google.com/forum/#!topic/comp.lang.python/PIkUno3avkw



I need help to increase the efficiency of this code : 


global repeat
repeat=1
def main():
    c=int(raw_input("How many numbers do you want to work? (Min. 2 Max. 3) "))
    if c==2:
        x=int(raw_input("Enter the first number to be worked "))
        y=int(raw_input("Enter the second number to be worked "))
    elif c==3:
        x=int(raw_input("Enter the first number to be worked "))
        y=int(raw_input("Enter the second number to be worked "))
        z=int(raw_input("Enter the third number to be worked "))
    else:
        print "Invalid input.";raw_input("Press <enter> to close this window");exit()    
    p=int(raw_input("Do you want to divide, subtract, add or multiply these numbers? (1=divide, 2=subtract, 3=add, 4=multiply) "))
    if p==1 and c==2:
        print "The result is : ",x/y
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    elif p==1 and c==3:
        print "The result is : ",x/y/z
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    elif p==2 and c==2:
        print "The result is : ",x-y
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    elif p==2 and c==3:
        print "The result is : ",x-y-z
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    elif p==3 and c==2:
        print "The result is : ",x+y
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    elif p==3 and c==3:
        print "The result is : ",x+y+z
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    elif p==4 and c==2:
        print "The result is : ",x*y
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    elif p==4 and c==3:
        print "The result is : "+str(x*y*z) 
        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
        if repeat==1:
            main()
    else:
        repeat=int(raw_input("Invalid Input. Please read instructions properly. Would you like to try again? Yes=1 No=2 "))
        if repeat==1:
            main()
        else:
            exit()
main()



Is there any way to make it smaller? It does it's job, but I want it to look smaller, more efficient.

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#55307

FromChris Angelico <rosuav@gmail.com>
Date2013-10-02 21:01 +1000
Message-ID<mailman.611.1380711666.18130.python-list@python.org>
In reply to#55303
On Wed, Oct 2, 2013 at 8:44 PM, JonDoe297 <vignesh.harikrishna@gmail.com> wrote:
> Is there any way to make it smaller? It does it's job, but I want it to look smaller, more efficient.

Yes, it is, but let me first clarify something: "Smaller" and "more
efficient" are two quite different concepts. Efficiency doesn't matter
to your code here, so what you're looking for is smaller, clearer
code. Which is a good thing to be doing :)

At top level, the 'global' declaration doesn't do anything. You may as
well not bother with it.

If you change your recursive main() function into a while loop, you'll
be able to combine all your common code very easily. I won't do the
whole job for you, but consider this structure:

repeat=1
while repeat==1:
    # get inputs
    # calculate and produce output
    repeat=int(raw_input("Do you want to do more? "))

And if you need your error state to have a different prompt, you can
use 'continue' to skip the bottom of the loop.

Hope that helps!

ChrisA

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#55338

FromJonDoe297 <vignesh.harikrishna@gmail.com>
Date2013-10-02 06:43 -0700
Message-ID<53e42327-366c-42ea-b111-0e98aefc8cef@googlegroups.com>
In reply to#55307
On Wednesday, October 2, 2013 4:31:03 PM UTC+5:30, Chris Angelico wrote:
> On Wed, Oct 2, 2013 at 8:44 PM, JonDoe297 wrote:
> 
> > Is there any way to make it smaller? It does it's job, but I want it to look smaller, more efficient.
> 
> 
> 
> Yes, it is, but let me first clarify something: "Smaller" and "more
> 
> efficient" are two quite different concepts. Efficiency doesn't matter
> 
> to your code here, so what you're looking for is smaller, clearer
> 
> code. Which is a good thing to be doing :)
> 
> 
> 
> At top level, the 'global' declaration doesn't do anything. You may as
> 
> well not bother with it.
> 
> 
> 
> If you change your recursive main() function into a while loop, you'll
> 
> be able to combine all your common code very easily. I won't do the
> 
> whole job for you, but consider this structure:
> 
> 
> 
> repeat=1
> 
> while repeat==1:
> 
>     # get inputs
> 
>     # calculate and produce output
> 
>     repeat=int(raw_input("Do you want to do more? "))
> 
> 
> 
> And if you need your error state to have a different prompt, you can
> 
> use 'continue' to skip the bottom of the loop.
> 
> 
> 
> Hope that helps!
> 
> 
> 
> ChrisA

Thanks a lot again Chris! You understood what I couldn't convey, perfectly! I'll use your suggestions ;)

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#55391

FromDennis Lee Bieber <wlfraed@ix.netcom.com>
Date2013-10-02 19:47 -0400
Message-ID<mailman.661.1380757646.18130.python-list@python.org>
In reply to#55303
On Wed, 2 Oct 2013 03:44:24 -0700 (PDT), JonDoe297
<vignesh.harikrishna@gmail.com> declaimed the following:

>
>global repeat

	This does nothing at the top level of a module

>repeat=1
>def main():
>    c=int(raw_input("How many numbers do you want to work? (Min. 2 Max. 3) "))

	You don't handle the case where someone enter a non-integer item

>    if c==2:
>        x=int(raw_input("Enter the first number to be worked "))
>        y=int(raw_input("Enter the second number to be worked "))
>    elif c==3:
>        x=int(raw_input("Enter the first number to be worked "))
>        y=int(raw_input("Enter the second number to be worked "))
>        z=int(raw_input("Enter the third number to be worked "))

	You duplicate the first two inputs -- yet by your definition, two is
the minimum. And since 3 is the maximum...

	x = int(....)
	y = int(....)
	if c == 3:
		z = int(....)


>    else:
>        print "Invalid input.";raw_input("Press <enter> to close this window");exit()    
>    p=int(raw_input("Do you want to divide, subtract, add or multiply these numbers? (1=divide, 2=subtract, 3=add, 4=multiply) "))
>    if p==1 and c==2:
>        print "The result is : ",x/y
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    elif p==1 and c==3:
>        print "The result is : ",x/y/z
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    elif p==2 and c==2:
>        print "The result is : ",x-y
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    elif p==2 and c==3:
>        print "The result is : ",x-y-z
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    elif p==3 and c==2:
>        print "The result is : ",x+y
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    elif p==3 and c==3:
>        print "The result is : ",x+y+z
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    elif p==4 and c==2:
>        print "The result is : ",x*y
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    elif p==4 and c==3:
>        print "The result is : "+str(x*y*z) 
>        repeat=int(raw_input("Do you want to calculate for more numbers? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>    else:
>        repeat=int(raw_input("Invalid Input. Please read instructions properly. Would you like to try again? Yes=1 No=2 "))
>        if repeat==1:
>            main()
>        else:
>            exit()
>main()
>
	Ack! way too many conditionals... Condense out the logic -- since you
apply the same operator to all data you just need a way to pass the
operator to a function that applies it to all the data.



-=-=-=-=-=-
import sys

while True:
    try:
        numItems = int(raw_input("\n\nHow many values? "))
    except:     #naked exception is not really good programming
        print "Invalid input, exiting..."
        sys.exit(1)

    print numItems
    
    items = []
    while len(items) < numItems:
        try:
            item = int(raw_input("Enter item #%s> " % (len(items) + 1)))
            items.append(item)
        except:     #see previous comment
            print "Invalid input, try again"

    oper = None
    while oper is None:
        oper = raw_input("Enter operation [+, -, *, /]> ")
        if oper[0] in "+-*/":
            oper = oper[0]
        else:
            oper = None

    #note -- I'm too lazy to look up the operator module, but the
    #above could have used a dictionary look-up to assign the
    #actual function to oper, and then the following if-block
    #becomes a simple
    #       cumulative = oper(cumulative, item)
    
    cumulative = items[0]
    for item in items[1:]:
        if oper == "+":
            cumulative += item
        elif oper == "-":
            cumulative -= item
        elif oper == "*":
            cumulative *= item
        elif oper == "/":
            cumulative /= item
        else:
            print "Programming Error -- operator is invalid after passing
check"

    print "Cumulative result is %s" % cumulative


-=-=-=-=-=-=-
C:\Users\Wulfraed\Documents>oper.py


How many values? 3
3
Enter item #1> 21
Enter item #2> 32
Enter item #3> 43
Enter operation [+, -, *, /]> +
Cumulative result is 96


How many values? 4
4
Enter item #1> 999
Enter item #2> 321
Enter item #3> 123
Enter item #4> 42
Enter operation [+, -, *, /]> -
Cumulative result is 513


How many values? 2
2
Enter item #1> 4737
Enter item #2> 121
Enter operation [+, -, *, /]> *
Cumulative result is 573177


How many values?
Invalid input, exiting...

C:\Users\Wulfraed\Documents>
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#55393

FromChris Angelico <rosuav@gmail.com>
Date2013-10-03 10:25 +1000
Message-ID<mailman.663.1380759957.18130.python-list@python.org>
In reply to#55303
On Thu, Oct 3, 2013 at 9:47 AM, Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:
>     try:
>         numItems = int(raw_input("\n\nHow many values? "))
>     except:     #naked exception is not really good programming
>         print "Invalid input, exiting..."
>         sys.exit(1)

Please don't _ever_ advocate this programming style! Wrapping
something in a try/except that emits a generic message and terminates
is a bad idea - the default behaviour, if you simply let the exception
happen, is to emit a very useful message and terminate. Never test for
any error condition you're not prepared to handle, as the BOFH advised
his boss.

ChrisA

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#55446

FromDennis Lee Bieber <wlfraed@ix.netcom.com>
Date2013-10-03 19:15 -0400
Message-ID<mailman.698.1380842159.18130.python-list@python.org>
In reply to#55303
On Thu, 3 Oct 2013 10:25:47 +1000, Chris Angelico <rosuav@gmail.com>
declaimed the following:

>On Thu, Oct 3, 2013 at 9:47 AM, Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:
>>     try:
>>         numItems = int(raw_input("\n\nHow many values? "))
>>     except:     #naked exception is not really good programming
>>         print "Invalid input, exiting..."
>>         sys.exit(1)
>
>Please don't _ever_ advocate this programming style! Wrapping
>something in a try/except that emits a generic message and terminates
>is a bad idea - the default behaviour, if you simply let the exception
>happen, is to emit a very useful message and terminate. Never test for
>any error condition you're not prepared to handle, as the BOFH advised
>his boss.
>
	Note: I DID include a comment that this was NOT good style.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#55453

FromChris Angelico <rosuav@gmail.com>
Date2013-10-04 16:45 +1000
Message-ID<mailman.708.1380869161.18130.python-list@python.org>
In reply to#55303
On Fri, Oct 4, 2013 at 9:15 AM, Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:
> On Thu, 3 Oct 2013 10:25:47 +1000, Chris Angelico <rosuav@gmail.com>
> declaimed the following:
>
>>On Thu, Oct 3, 2013 at 9:47 AM, Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:
>>>     try:
>>>         numItems = int(raw_input("\n\nHow many values? "))
>>>     except:     #naked exception is not really good programming
>>>         print "Invalid input, exiting..."
>>>         sys.exit(1)
>>
>>Please don't _ever_ advocate this programming style! Wrapping
>>something in a try/except that emits a generic message and terminates
>>is a bad idea - the default behaviour, if you simply let the exception
>>happen, is to emit a very useful message and terminate. Never test for
>>any error condition you're not prepared to handle, as the BOFH advised
>>his boss.
>>
>         Note: I DID include a comment that this was NOT good style.

You mentioned that bare except is a problem; I'm more looking at the
fact that the except clause simply writes a message and terminates.
They're two separate issues, both bad style.

I know _you_ know it's bad style; but someone reading over this needs
to be aware that this shouldn't normally be done.

ChrisA

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