How to increment every time a class instance is called

Question

I am learning more about OOP in Python and I have hit a bit of a road block. Below is my code:

class Player: bats = 0 hit = 0 freePass = 0 out = 0 defenseError = 0 def __init__(self, name): self.name = name Player.hit+=1 Player.freePass+=1 Player.out+=1 Player.defenseError+=1 #-------------------------------- def main(): steve = Player("steve") steve.hit steve.hit steve.hit #-------------------------------- main()

As you can tell, I have created a class that is supposed to increment a counter every time an instance is called in the main function. For example, 'steve.hit' is called three different times, so the hit counter should increment to 3. I have attempted many different ways of approaching this; but every time I try something, instead of counting the three different calls as such, the program will only count the three calls as one. Thank you for any help you can give me

"steve.hit" isn't a "call", it's just accessing an attribute. That won't execute __init__. Either make it an actual function call (e.g. steve.hit()) in which you can do whatever you want, or make it a @property which allows you to do a function call simply when doing steve.hit. — deceze
– deceze ♦, Commented Oct 24, 2018 at 0:52

U13-Forward · Accepted Answer · 2018-10-24 01:05:22Z

I would prefer the below for calss:

class Player: def __init__(self, name): self.name = name self.bats_ = 0 self.hit_ = 0 self.freePass_ = 0 self.out_ = 0 self.defenseError_ = 0 def hit(self): self.hit_+=1 def freePass(self): self.freePass_+=1 def out(self): self.out_+=1 def defenseError(self): self.defenseError_+=1

Make self instead of Player, and make functions for them,

Then call it like (see comments):

def main(): steve = Player("steve") # Create a player steve.hit() # add 1 to `hit` steve.hit() # add 1 to `hit` again steve.hit() # add 1 to `hit` again return steve.hit_ # to return, use `_hit` because in `__init__`, it's called `hit_`, which is added always

Now:

print(main())

Outputs:

Yey!!, it's as expected.

Or even better @property:

So class would be:

class Player: def __init__(self, name): self.name = name self.bats_ = 0 self.hit_ = 0 self.freePass_ = 0 self.out_ = 0 self.defenseError_ = 0 @property def hit(self): self.hit_+=1 @property def freePass(self): self.freePass_+=1 @property def out(self): self.out_+=1 @property def defenseError(self): self.defenseError_+=1

Then to call it (no need to call just type it without parenthesis):

def main(): steve = Player("steve") steve.hit steve.hit steve.hit return steve.hit_

Now:

print(main())

Outputs:

Yey!!, it's as expected.

carlos_fab · Accepted Answer · 2018-10-24 01:29:40Z

First thing, you need to instantiate you class. This effectively means to go and build an object (Player) based on the plan that you defined in the class. You do that just by declaring a new variable, steve = Player("steve")

The __init__ method is a special method that gets called automatically when you create a new object. Here, your class takes only one argument, name. All other variables like hit are assigned automatically to 0.

If you want to change the value of hit, you should create a function (also known as a method. Then you call this method quite simply with steve.increment_hit().

class Player(): """Class to represent a player.""" def __init__(self, name): self.name = name self.hit = 0 self.bats = 0 self.freePass = 0 self.out = 0 self.defenseError = 0 def increment_hit(self): """Increase hit count by one when called.""" self.hit += 1 # instantiate your class steve = Player("steve") print("Hits for '{}' after instantiate your class: {}\n".format(steve.name, steve.hit)) # call the increase_hit method 3 times for i in range(3): steve.increment_hit() print("Hits for player {}: {}".format(steve.name, steve.hit))

Try always change the value of variables by calling a method, never by accessing the variable itself directly.

Is better use steve.increment_hit() than accessing class variables directly with steve.hit += 1, for example.

After run the code above, you will get this output:

 Hits for 'steve' after instantiate your class: 0 Hits for player steve: 1 Hits for player steve: 2 Hits for player steve: 3

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