You need to pass some data into it. An empty dictionary, for example.
if __name__ == '__main__': DHT('a').showData()
However, in your example a parameter is not even needed. You can declare it by just:
def __init__(self):
Maybe you mean to set it from the data?
class DHT:
def __init__(self, data):
self.data['one'] = data['one']
self.data['two'] = data['two']
self.data['three'] = data['three']
def showData(self):
print(self.data)
if __name__ == '__main__': DHT({'one':2, 'two':4, 'three':5}).showData()
showData
will print the data you just entered.