Python calling function with return statement

Question

I have the below piece that created few person objects and apply some methods on those objects.

class Person:
    def __init__(self, name, age, pay=0, job=None):
        self.name = name
        self.age  = age
        self.pay  = pay
        self.job  = job

    def lastname(self):
        return  self.name.split()[-1]

    def giveraise(self,percent):
        return self.pay *= (1.0 + percent)

if __name__ == '__main__':
    bob = Person('Bob Smith', 40, 30000, 'software')
    sue = Person('Sue Jones', 30, 40000, 'hardware')
    people = [bob,sue]
    print(bob.lastname())
    print(sue.giveraise(.10))

Once I run this program, this is the output--

Syntax Error: Invalid syntax

but when I run using the below code, I don't have any problem,

if __name__ == '__main__':
    bob = Person('Bob Smith', 40, 30000, 'software')
    sue = Person('Sue Jones', 30, 40000, 'hardware')
    people = [bob,sue]
    print(bob.lastname())
    sue.giveraise(.10)
    print(sue.pay)

What is the difference in two cases

Where do you receive the SyntaxError? Please update your question with the full Traceback of the error message. — Joel Cornett
– Joel Cornett, Commented Jun 3, 2012 at 2:35
From a design standpoint, unless you have a very good reason for doing so, giveraise() shouldn't return a value. "Give raise" implies you are acting on the data in the class instance. It would make more sense to have a separate property accessor for post-raise pay. — Joel Cornett
– Joel Cornett, Commented Jun 3, 2012 at 2:41

BrenBarn · Accepted Answer · 2012-06-03 02:34:15Z

5

*= is an assignment, and assignment is a statement in Python, not an expression. Try:

self.pay *= (1.0 + percent)
return self.pay

answered Jun 3, 2012 at 2:34

BrenBarn

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Comments

Mark Reed · Accepted Answer · 2012-06-03 02:36:50Z

1

I get the invalid syntax error even in the second version; I don't know how you got it to work, but you must have changed the giveraise function. In Python, assignments, including those using mutators like *=, are statements, not expressions; they have no value. Since they have no value, it doesn't make sense to return them from a function, hence the error.

answered Jun 3, 2012 at 2:36

Mark Reed

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Comments

Blender · Accepted Answer · 2012-06-03 02:34:12Z

0

Your problem is this function (I get an error in both cases):

def giveraise(self,percent):
    return self.pay *= (1.0 + percent)

Change it to this and it will work:

def giveraise(self,percent):
    self.pay *= (1.0 + percent)
    return self.pay

I'm not entirely sure why Python throws a syntax error, but I do know that this works.

answered Jun 3, 2012 at 2:34

Blender

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1 Comment

C0deH4cker Over a year ago

Assignments in Python do not return the value, which is why you can't do this: if((line = myFile.readline())): #stuff here.... This type of code works in C, but not in Python. This is part of the plan for Python to be easily readable.

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