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To: python-list@python.org
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: Efficency help for a Calculator Program
Date: Wed, 02 Oct 2013 19:47:15 -0400
Organization: IISS Elusive Unicorn
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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/