TypeError: Missing 1 required positional argument: 'self'

Question

I am new to python and have hit a wall. I followed several tutorials but cant get past the error:

Traceback (most recent call last):
  File \"C:\\Users\\Dom\         


        

Answer 1

Works and is simpler than every other solution I see here :

Pump().getPumps()

This is great if you don't need to reuse a class instance. Tested on Python 3.7.3.

Answer 2

You need to instantiate a class instance here.

Use

p = Pump()
p.getPumps()

Small example -

>>> class TestClass:
        def __init__(self):
            print("in init")
        def testFunc(self):
            print("in Test Func")


>>> testInstance = TestClass()
in init
>>> testInstance.testFunc()
in Test Func

Answer 3

The self keyword in Python is analogous to this keyword in C++ / Java / C#.

In Python 2 it is done implicitly by the compiler (yes Python does compilation internally). It's just that in Python 3 you need to mention it explicitly in the constructor and member functions. example:

 class Pump():
 //member variable
 account_holder
 balance_amount

   // constructor
   def __init__(self,ah,bal):
   |    self.account_holder = ah
   |    self.balance_amount = bal

   def getPumps(self):
   |    print("The details of your account are:"+self.account_number + self.balance_amount)

 //object = class(*passing values to constructor*)
 p = Pump("Tahir",12000)
 p.getPumps()

Answer 4

You can call the method like pump.getPumps(). By adding @classmethod decorator on the method. A class method receives the class as the implicit first argument, just like an instance method receives the instance.

class Pump:

def __init__(self):
    print ("init") # never prints

@classmethod
def getPumps(cls):
            # Open database connection
            # some stuff here that never gets executed because of error

So, simply call Pump.getPumps() .

In java, it is termed as static method.

Answer 5

You need to initialize it first:

p = Pump().getPumps()

Answer 6

You can also get this error by prematurely taking PyCharm's advice to annotate a method @staticmethod. Remove the annotation.