I wrote a function which gets two numbers and an operation (string) and returns the result of the two numbers with the given operation. For example calculate_matehamatical_expression(5,6,'+') should return 11. I divide the the assignment to little functions, but when I call these little function it always returns None. Can someone explain to me why that happens? This is the Code I wrote:
def mathematical_sum(num1,num2):
return num1 + num2
def mathematical_difference(num1,num2):
return num1 - num2
def mathematical_product(num1,num2):
return num1 * num2
def mathematical_division(num1,num2):
if num2 != 0:
return num1 / num2
else:
return None
def operation_error(operation):
if operation != "+" or operation != "-" or operation != "*" or operation != "/":
return None
def calculate_mathematical_expression(num1,num2,operation):
if operation == "+":
mathematical_sum(num1,num2)
elif operation == "-":
mathematical_difference(num1,num2)
elif operation == "*":
mathematical_product(num1,num2)
elif operation == "/":
mathematical_division(num1,num2)
else:
operation_error(operation)
You need to return again inside calculate_mathematical_expression
, eg:
def calculate_mathematical_expression(num1,num2,operation):
if operation == "+":
return mathematical_sum(num1,num2)
The return in mathematical_sum
doesn't affect the function it's being called from.
return
When you return
from a function, it only returns to the function that called it. So when you return
in mathematical_sum()
, the value is returned to calculate_mathematical_expression()
& you need to return again from this function, like this:
if operation == "+":
return mathematical_sum(num1,num2)
elif operation == "-":
return mathematical_difference(num1,num2)
elif operation == "*":
return mathematical_product(num1,num2)
elif operation == "/":
return mathematical_division(num1,num2)
else:
return operation_error(operation)
...otherwise calculate_mathematical_expression()
returns None
.
operation_error()
does not work and
instead of or
. Otherwise your condition will always be True
None
. Here, your function always return None
Example:
def operation_error(operation):
return operation != "+" and operation != "-" and operation != "*" and operation != "/"
operation_error()
Since you have a condition for each operator, you don't need the operation_error()
function, you can directly do this:
else:
return None
...or even remove the else
statement and let calculate_mathematical_expression()
automatically return None
when reaching its end.
Your calculate_mathematical_expression function is not returning anything. Try following code:
def calculate_mathematical_expression(num1,num2,operation):
if operation == "+":
return mathematical_sum(num1,num2)
elif operation == "-":
return mathematical_difference(num1,num2)
elif operation == "*":
return mathematical_product(num1,num2)
elif operation == "/":
return mathematical_division(num1,num2)
else:
return operation_error(operation)
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