This question already has answers here:
Why does "a == x or y or z" always evaluate to True? How can I compare "a" to all of those?
(8 answers)
Closed 3 years ago.
I'm new to python and am trying to make a basic calculator that takes two numbers and performs the operation specified by the user, but regardless of the operation I enter, the numbers always add.
num1 = int(input("Enter a number. "))
print(" ")
num2 = int(input("Enter another number. "))
print(" ")
operation = input("Type Add, Subtract, Multiply, or Divide" )
if operation == "Add" or "add":
add = num1 + num2
print(add)
elif operation == "Subtract" or "subtract":
sub = num1 - num2
print(sub)
elif operation == "Multiply" or "multiply":
mult = num1 * num2
print(mult)
elif operation == "Divide" or "divide":
div = num1 / num2
print(div)
else:
print("Enter a valid operation: ")
With what I have, if num1 = 10 and num2 = 5 and I enter "multiply" the result I get is 15, not 50.
if operation == "Add" or "add"
These are two conditions:
if operation == "Add" which does what you expect.
if "add" - Always evaluates to True because it's a constant string.
So you could just as well have written:
if True. You need to replace it with:
if operation == "Add" or operation == "add"
Anyway, I would like to suggest a few things.
Lowercase then check only once
You should lowercase your input string instead of double checking "Add" or "add":
num1 = int(input("Enter a number. "))
print(" ")
num2 = int(input("Enter another number. "))
print(" ")
operation = input("Type Add, Subtract, Multiply, or Divide" ).lower() # Notice the `lower` here
if operation == "add":
add = num1 + num2
print(add)
elif operation == "subtract":
sub = num1 - num2
print(sub)
elif operation "multiply":
mult = num1 * num2
print(mult)
elif operation "divide":
div = num1 / num2
print(div)
else:
print("Enter a valid operation: ")
Use the built-in operator module
The operator module contains exactly the methods that you seek for. You could use it for convenience (haven't tested, should work):
import operator
keywords = {"add": "add", "subtract": "sub", "multiply": "mul", "divide": "truediv"}
num1 = int(input("Enter a number. "))
print(" ")
num2 = int(input("Enter another number. "))
print(" ")
operation = input("Type Add, Subtract, Multiply, or Divide" )
op_func = keywords.get(operation.lower(), "add") # defaults to add
print(getattr(operator, op_func)(num1, num2))
def fun(operation, num1,num2):
operation = operation.lower()
if operation == "add":
add = num1 + num2
print(add)
elif operation == "subtract":
sub = num1 - num2
print(sub)
elif operation == "multiply":
mult = num1 * num2
print(mult)
elif operation == "divide":
div = num1 / num2
print(div)
else:
print("Enter a valid operation: ")
fun('multiply', 10,5)
Why:
if operation == "add" or "Add": this is always True
We can use if operation == "add" or operation == "Add":
You have to do like this:
num1 = int(input("Enter a number. "))
print(" ")
num2 = int(input("Enter another number. "))
print(" ")
operation = str(input("Type Add, Subtract, Multiply, or Divide" ))
if operation == "Add" or operation =="add":
add = num1 + num2
print(add)
elif operation == "Subtract" or operation =="subtract":
sub = num1 - num2
print(sub)
elif operation == "Multiply" or operation =="multiply":
mult = num1 * num2
print(mult)
elif operation == "Divide" or operation =="divide":
div = num1 / num2
print(div)
else:
print("Enter a valid operation: ")
Because of or operation with string, all your conditions will be true.
That's why it will only go to first condition no matter what you give in the input.
Related
This question already has answers here:
What does "while True" mean in Python?
(18 answers)
Closed 2 years ago.
when i run this code it keeps on giving me the answer
here is my code
num1 = float(raw_input("enter a number: ")) # type: float
operation = str(raw_input("enter a operation: "))
num2 = float(raw_input("enter a number: ")) # type: float
while True:
if operation == "+":
print num1 + num2
elif operation == "-":
print num1 - num2
elif operation == "*":
print num1 * num2
elif operation == "/":
print (num1 / num2)
else:
print("Error Error")
What you might want is to put the input taking code into the while loop:
while True:
num1 = float(raw_input("enter a number: ")) # type: float
operation = str(raw_input("enter a operation: "))
num2 = float(raw_input("enter a number: ")) # type: float
if operation == "+":
print (num1 + num2)
elif operation == "-":
print (num1 - num2)
elif operation == "*":
print (num1 * num2)
elif operation == "/":
print (num1 / num2)
else:
print("Error Error")
`while True:` means Infinite Loop.
You can take input inside while loop or you can change the condition of while loop.
remove the while True: and it will only print out the answer once. while loops continue running as long as the argument is true and True is always true :P
What you probably want is for the application to keep calculating input from the user.
Try this
def calculate():
num1 = float(raw_input("enter a number: ")) # type: float
operation = str(raw_input("enter a operation: "))
num2 = float(raw_input("enter a number: ")) # type: float
if operation == "+":
print (num1 + num2)
elif operation == "-":
print (num1 - num2)
elif operation == "*":
print (num1 * num2)
elif operation == "/":
print (num1 / num2)
else:
print("Error Error")
while True:
calculate()
This question already has answers here:
Correct way to write line to file?
(17 answers)
Closed 2 years ago.
f = open("calculator.txt", "a+")
a = True
while a == True:
operation = input("Please input an operation (+, -, *, /): ")
num1 = float(input("Please input number 1: "))
num2 = float(input("Please input number 2: "))
if operation == "+":
result = num1 + num2
elif operation == "-":
print(num1 - num2)
elif operation == "*":
print(num1 * num2)
elif operation == "/":
print(num1 / num2)
answer = input("Run again? (Yes/No): ")
if answer == "Yes":
continue
else:
print("Goodbye ")
exit()
How do i go about writing the results of the calculations in a file? Say the user inputs 5 + 5 and the program returns 10, how would I save "10" in a text file? If possible the entire equation "5+5 = 10"
You can use str.format to format result string and then use print() with file= parameter to write to file. For example:
with open('operations.txt', 'a') as f_out:
while True:
operation = input("Please input an operation (+, -, *, /): ")
num1 = float(input("Please input number 1: "))
num2 = float(input("Please input number 2: "))
if operation == "+":
result = num1 + num2
elif operation == "-":
result = num1 - num2
elif operation == "*":
result = num1 * num2
elif operation == "/":
result = num1 / num2
result_string = '{} {} {} = {}'.format(num1, operation, num2, result)
# print result string to screen:
print(result_string)
# save result string to file
print(result_string, file=f_out)
answer = input("Run again? (Yes/No): ")
if answer == "Yes":
continue
else:
print("Goodbye ")
break
Prints:
Please input an operation (+, -, *, /): +
Please input number 1: 1
Please input number 2: 2
1.0 + 2.0 = 3.0
Run again? (Yes/No): Yes
Please input an operation (+, -, *, /): /
Please input number 1: 2
Please input number 2: 4
2.0 / 4.0 = 0.5
Run again? (Yes/No): no
Goodbye
And saves operations.txt:
1.0 + 2.0 = 3.0
2.0 / 4.0 = 0.5
You could do it like this:
f.write(f'{num1} {operation} {num2} = {result}') # for example, '5 + 5 = 10'
if answer == "Yes":
continue
else:
print("Goodbye ")
you can change your program like this:
f = open("calculator.txt", "a+")
a = True
while a:
operation = input("Please input an operation (+, -, *, /): ")
num1 = float(input("Please input number 1: "))
num2 = float(input("Please input number 2: "))
if operation == "+":
result = num1 + num2
elif operation == "-":
result = num1 - num2
elif operation == "*":
result = num1 * num2
elif operation == "/":
result = num1 / num2
print(result)
f.write(f"{num1}{operation}{num2} = {result}\n") #this will save the whole equation
answer = input("Run again? (Yes/No): ")
if answer == "Yes":
continue
else:
print("Goodbye ")
a = False
Just do like this:
with open("calculator.txt", "a+") as myfile:
myfile.write("\n" + result)
Inside if block
You can open the file and write into it like this:
f = open("calculator.txt", "a+")
f.write(f"{num1} {operation} {num2} = {result}")
I am a beginner to Python and have just started learning recently.
After learning about if, elif and else statements I decided to try and make a simple calculator.
Now, a few hours later I was wondering how I could improve it and make it more complex.
I am trying to store the result of the addition, subtraction, divison or multiplication of the first two numbers in a variable. After doing this I want to Re-create the calculator only I already have the first number.
I am also running into problems with my continue1 if statement, for some reason even if the user inputs "no" the script continues instead of displaying a message.
I'd really appreciate any help at all, Thank you!
Python code:
num1 = float(input("Please enter your first number: "))
num2 = float(input("Please enter your second number: "))
operator = input("Please enter operator: ")
if operator == "/":
print(num1 / num2)
elif operator == "+":
print(num1 + num2)
elif operator == "-":
print(num1 - num2)
elif operator == "*":
print(num1 * num2)
else:
print("FATAL ERROR")
num3 = num1 / num2
num3 = num1 - num2
num3 = num1 + num2
num3 = num1 * num2
continue1 = input ("Would you like too continue? [Yes/No]")
if continue1 == "yes" or "Yes":
operator1 = num4 = float(input("Please enter second number: "))
else:
print("Fatal error")
input("please enter operator")
if operator == "/":
print(num3 / num4)
elif operator == "+":
print(num3 + num4)
elif operator == "-":
print(num3 - num4)
elif operator == "*":
print(num3 * num4)
else:
print("Please press enter to close.")
input("Press Enter to Exit")
In the first part, just assign to a variable (and then print it if you want):
if operator == "/":
num3 = num1 / num2
elif operator == "+":
num3 = num1 + num2
elif operator == "-":
num3 = num1 - num2
elif operator == "*":
num3 = num1 * num2
else:
print("FATAL ERROR")
print(num3)
Regarding the second part of your question, in your statement:
if continue1 == "yes" or "Yes":
this is wrong because or is an operator which will combine the two things on either side of it (typically used where each of these two things is something that evaluates to True or False), so you could have for example:
if continue1 == "yes" or continue1 == "Yes":
You can also add brackets to control the order of execution, as shown below. In this case they do not affect the result, because it is already the case that the == operators are evaluated before the or, but they may make it clearer to read.
if (continue1 == "yes") or (continue1 == "Yes"):
You can also do this instead:
if continue1 in ("yes", "Yes"):
The details of what is going wrong with your original form of the conditional statement are perhaps not important at this stage, but I mention them for sake of completeness. If you enter "No" then the whole expression will actually evaluate to "Yes" (the continue1 == "yes" evaluates to False, and then False or "Yes" evalues to "Yes"). The if statement then treats the value "Yes" (a non-empty string) as a true value and so executes the code which depends on the condition.
num1 = float(input("Please enter your first number: "))
num2 = float(input("Please enter your second number: "))
keepCalculate=True
while keepCalculate:
operator = input("Please enter operator: ")
if operator == "/":
print(num1 / num2)
elif operator == "+":
print(num1 + num2)
elif operator == "-":
print(num1 - num2)
elif operator == "*":
print(num1 * num2)
else:
print("FATAL ERROR")
continue1 = input ("Would you like too continue? [Yes/No]")
if continue1== "yes" or "Yes":
keepCalculate=True
else:
keepCalculate=False
The most simple way todo what you want
simply use
num3 = num1 + num2
to store the codes
"or" in programming doesn't work like or in rel life, it is ussed to separate 2 different conditions, hence use:
if continue1 == "yes" or continue1 == "Yes":
I recreated your code now it's working:
def op(operator,num1,num2):
global num3
if operator == "/":
num3 = num1 / num2
elif operator == "+":
num3 = num1 + num2
elif operator == "-":
num3 = num1 - num2
elif operator == "*":
num3 = num1 * num2
else:
print("FATAL ERROR")
num1 = float(input("Please enter your first number: "))
num2 = float(input("Please enter your second number: "))
operator = input("Please enter operator: ")
op(operator,num1,num2)
print(num3)
continue1 = input ("Would you like too continue? [Yes/No]").lower()
if continue1 in ["yes", "y"]:
num4 = float(input("Please enter second number: "))
operator = input("please enter operator")
op(operator,num3,num4)
print(num3)
else:
print("Fatal error")
input("Press Enter to Exit")
Whatever you do, this code will keep as result, the value of num3 = num1 * num2. You should put these lines in each if, elif
I'm working on this calculator but the output that I keep getting is function ops at 0x03B0B858 instead of it being a number, and i'm not really sure what i'm doing wrong....
The calculator asks three questions, first number, operator, and the second number. if you type in letters or anything other than numbers when asked the first number and the second number, it will tell you that what you typed in was invalid and asks you to enter a valid number again, the problem is that I'm trying to do that with the operator as well which is defined inside the function ops() but it doesn't matter what I typed in the operator the result will always be random letters and numbers.... This is the code below, you can copy past it and try it and see what I mean by all of this..
try:
num1 = float(input('Enter the first number: '))
except ValueError:
print('Invalid number')
num1 = float(input('Enter first number again: '))
op = input('Enter operator: ')
try:
num2 = float(input('Enter the second number: '))
except ValueError:
print('Invalid number')
num2 = float(input('Enter second number again: '))
def ops():
if op != '+' or '-' or '/' or '*':
op = input('Invalid Operator, please enter operator: ')
elif op == '+':
return num1 + num2
elif op == '-':
return num1 - num2
elif op == '*':
return num1 * num2
elif op == '/':
return num1 / num2
print(ops)
First:
- to run the function 'ops' you should call print(ops()) , do not forget the parentheses
- try putting the code inside the function, otherwise, your function won't recognize the variable 'op'
- you cannot check the content of the variable 'op' like that
op != '+' or '-' or '/' or '*'
this will be evaluated as a single boolean 'OR',
your code should go like that instead:
if op not in ['+' , '-' , '/' , '*']:
do smthg...
Edit 2:
Complete solution:
def ops():
try:
num1 = float(input('Enter the first number: '))
except ValueError:
print('Invalid number')
num1 = float(input('Enter first number again: '))
op = input('Enter operator:')
try:
num2 = float(input('Enter the second number: '))
except ValueError:
print('Invalid number')
num2 = float(input('Enter second number again: '))
if op not in ['+' , '-' , '/' , '*']:
op = input('Invalid Operator, please enter operator: ')
if op == '+':
return num1 + num2
elif op == '-':
return num1 - num2
elif op == '*':
return num1 * num2
elif op == '/':
return num1 / num2
print(ops())
I can't quite figure out why my code won't work.
Whenever I click run, it doesn't follow back with a traceback error, it just says process finished with exit code 0.
I thought it might be the casefold but then when I applied it to "Y". casefold it wouldn't work full stop.
def calculate():
operator = input("please select the kind of maths you would like to do")
if operator == "+":
num1 = int(input('Enter first number: '))
num2 = int(input('Enter second number: '))
print('{} + {} ='.format(num1, num2))
print(num1 + num2)
elif operator == "-":
num1 = int(input("enter first number: "))
num2 = int(input("enter second number: "))
print("{} - {} =".format(num1, num2))
print(num1 - num2)
elif operator == "*":
num1 = int(input("enter first number: "))
num2 = int(input("enter second number: "))
print("{} * {} =".format(num1, num2))
print(num1 * num2)
elif operator == "/":
num1 = int(input("enter first number: "))
num2 = int(input("enter second number: "))
print("{} / {} =".format(num1, num2))
print(num1 / num2)
else:
_exit = input("would you like to exit? type Y for YES and N for NO")
if _exit.casefold() == "y":
sys.exit()
else:
calculate()
Just add calculate() at the very end to call the function.
Put function calling calculate() at the end without any indent. Your function isn't even getting called, thus giving no error.
You need to call this calculate() function first (at least it's not being executed in your code sample).
def calculate()
# func code here
#Exec this function
calculate()
I guess it should be like this:
def calculate():
operator = input("please select the kind of maths you would like to do")
if operator == "+":
num1 = int(input('Enter first number: '))
num2 = int(input('Enter second number: '))
print('{} + {} ='.format(num1, num2))
print(num1 + num2)
elif operator == "-":
num1 = int(input("enter first number: "))
num2 = int(input("enter second number: "))
print("{} - {} =".format(num1, num2))
print(num1 - num2)
elif operator == "*":
num1 = int(input("enter first number: "))
num2 = int(input("enter second number: "))
print("{} * {} =".format(num1, num2))
print(num1 * num2)
elif operator == "/":
num1 = int(input("enter first number: "))
num2 = int(input("enter second number: "))
print("{} / {} =".format(num1, num2))
print(num1 / num2)
else:
_exit = input("would you like to exit? type Y for YES and N for NO")
if _exit.casefold() == "y":
sys.exit()
else:
calculate()
calculate()