CODEWITHSUNDEEP
pythonpython-3.3
monkey334
monkey334

Reputation: 337

Python - When executing program via CMD, it just closes after the second input

import sys
import os
print ("Welcome to the Calculator")

def main():
    a = input ("Please enter the first operand: ")
    op = input ("Please enter the operation you wish to perform, +, -, *, / : ")
    b = input ("Please enter the second operand: ")

    a = int(a)
    b = int(b)

    if op == "+":
            ans = (a + b)

            print (ans)

    elif op == "-":
            ans = (a - b)
            print (ans)

    if op == "*":
            ans = (a * b)
            print (ans)

    elif op == "/":
            ans = (a / b)
            print (ans)

    again = input("Would you like to perform another calculation? Y or N?")

    if again == "Y":
            main()

main()

Hi, sorry for asking so many questions.

Basically, I put my code above, and upon executing the code by double clicking the .py file, which launches it off CMD, after being prompted with the message: "Please enter the operation you wish to perform, +, -, *, / :"

CMD just randomly closes itself. It's also happened to all my Python programs. Any ideas why? Is it to do with my terrible code?

All replies are much appreciated :)

Upvotes: 1

Views: 1437

Answers (4)

Anshul Goyal
Anshul Goyal

Reputation: 77007

You need to use raw_input() instead of input()

So make the following change

def main()
    ...
    op = raw_input ("Please enter the operation you wish to perform, +, -, *, / : ")
    ...

Upvotes: 4

Bakuriu
Bakuriu

Reputation: 101989

Assuming you are using python 2, and not 3.3

The problem is that the input function in python2 executes code. this means that when the user enters one of *, +, /, - an exception is raised(since +, or - or * or / aren't complete expressions or statements) and the program terminates, hence the CMD closes.

To check this try to wrap the input call in a try...except statement:

try:
    op = input('... * / - +')
except Exception:
    input('OPS!')   #just to verify that this is the case.

In particular this is what I get when trying to type + as input in python2:

>>> input('')
+
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1
    +
    ^
SyntaxError: unexpected EOF while parsing

In python2 you should use the raw_input function, which returns a string. In python3 raw_input was renamed to input, and thus your program runs fine and doesn't show the behaviour you describe.

Upvotes: 4

Infamouslyuseless
Infamouslyuseless

Reputation: 982

Try, under main(), write

input("\n\nPress the enter key to exit: ")

now it would have to wait for you to press enter so it passes bye that input and closes, try that, hope i helped :)

Upvotes: 3

Colonel Panic
Colonel Panic

Reputation: 1614

This has to do with how Windows handles the execution. The default is to close right away after the program has terminated. There may be a setting to fix this, but a quick solution is to open up Command Prompt, cd to the direction, and execute your script directly.

Upvotes: 2

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