Efficency help for a Calculator Program

[JonDoe297]

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.

 

[Chris Angelico]

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

 

[JonDoe297]

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

 

[Dennis Lee Bieber]

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>

 

[Chris Angelico]

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

 

[Dennis Lee Bieber]

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.

 

[Chris Angelico]

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