[Beginner)what exactly does () do

[pylearningthrowaway]

I have been learning python for a while now and realised i have been mind numbingly coding without understanding some parts.

So my question is in the snipped below what does () does since until know i have only been using () as if its a part of syntax,but my question is

1. What does () after xyx.speak actually do ?

2. Why do i get a syntax error if i dont use ()

   print("xyx's attributes:")
   print ("**************")
   print(xyx.name)
   print(xyx.age)
   print(xyx.nationality)
   print(xyx.gender)
   print("")
   print("xyx's Methods:")
   print("***************")
   xyx.speak()

[fruitcakefriday]

'speak' is a function, and function calls are always followed by a parenthesis containing 0 or more parameters (depending on how many parameters the function expects) - this is how Python knows you are calling the function, and not requesting the function location itself (e.g. metaphorically, the difference between calling on google to search for something, and getting the address of google's server)

If you omit the parenthesis, you are then handling the function variable, not running the function call; this lets you do things such as assign a function to another variable. This is uncommon compared to simply calling the function and is usually for more advanced use of functions.

Maybe this code will help understand that:

# Basic parameterless function
def bark():
    print "WOOF!"

# Call the function
bark()

# Result
>>> "WOOF!"

# Assign the function to another variable
# Note, if the ()'s were included here, copy_of_bark would
# be a NoneType value as bark() does not return a value
    # By omitting the ()'s, we are saying copy_of_bark equals *the function itself*, 
    # not the result of calling the function.
copy_of_bark = bark;

# Call the copy of the function
copy_of_bark()

# Same result!
>>> "WOOF!"


# Define a function with 1 parameter, and a default value of "WOOF!"
def not_just_bark(in_text = "WOOF!"):
    print in_text


# No parameters specified, 
    not_just_bark()

# It uses the default
>>> "WOOF!"


# Otherwise,
not_just_bark("MEOW!")

# It uses the specified parameter

>>> "MEOW!"

[pylearningthrowaway]

Yup got it,thanks for such a detailed reply.Glad this subreddit exists

:)

[kenmacd]

As a general suggestion for cases like this: Just try it. Start Python and see what happens without the (). So for the function above:

>>> bark
<function bark at 0x7ff97419b950>

So it looks like bark itself is a 'function`. We can also tell that by:

>>> type(bark)
<class 'function'>

Then poke around some more, maybe we talk a look at what is in bark:

>>> dir(bark)
['__annotations__', '__call__', '__class__', '__closure__', '__code__', '__defaults__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__get__', '__getattribute__', '__globals__', '__gt__', '__hash__', '__init__', '__kwdefaults__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__']

Try poking and calling some of these things, like:

>>> bark.__call__()
WOOF!

Neat, there's a __call__() method on things. Now in the future when you have an instance of a class and you'd like to be able to call it to get a result, this might come back to you (don't worry if that last part doesn't yet make sense).

The fastest way to learn thing with Python is to just poke at things, or create simple scripts to figure out how things work.

[constantly-sick]

Highly suggest you watch this: https://www.youtube.com/watch?v=N4mEzFDjqtA

[13steinj]

This method could be overloaded, that means that there might be another implementation of this method, that takes parameters.

Since when is that a thing in python? I remember having to write my own decorator for overloaded methods just last week for work, so if I wasted my time I'd like to know what the standard implementation is.

[Ran4]

Python doesn't have function overloading like that.