Instance-Level Methods

Instance-level methods are the most common type of method in Python. They are used to perform operations on an instance of a class and require the self parameter to access the instance’s attributes.

In the following example, the analyze method is an instance-level method because it needs to access specific instance data (self.data) that is created when the object is instantiated.

import pandas as pd

class DataAnalyzer:
    def __init__(self, data):
        self.data = data

    def analyze(self): # instance-level method
        print(f"Shape of data: {self.data.shape}")

data = pd.DataFrame({'a': [1, 2, 3], 'b': [4, 5, 6]})
analyzer = DataAnalyzer(data)
analyzer.analyze()

Output:

Shape of data: (3, 2)

Class Methods

Class methods, on the other hand, are methods that are bound to the class rather than an instance of the class. They are defined using the @classmethod decorator and are often used to provide alternative ways of constructing objects.

In the following code, the from_csv is a class method for several reasons:

• It serves as an alternative constructor – a different way to create an instance of DataAnalyzer
• It needs access to the class (cls) to create a new instance, but doesn’t need access to instance data

import pandas as pd

class DataAnalyzer:
    def __init__(self, data):
        self.data = data

    def analyze(self):
        print(f"Shape of data: {self.data.shape}")

    @classmethod
    def from_csv(cls, csv_path):  # class method
        data = pd.read_csv(csv_path)
        return cls(data)

Now, let’s use the from_csv class method to create an instance of the DataAnalyzer class by reading data from a CSV file. The from_csv method returns an instance of the DataAnalyzer class, which we can then use to call the analyze method.

# Using the class method to create an instance from a CSV file
csv_file_path = "data.csv"
analyzer = DataAnalyzer.from_csv(csv_file_path) 
analyzer.analyze()

Output:

Shape of data: (3, 4)

Conclusion

In conclusion, class methods provide an alternative way of constructing objects and can be used to perform operations that don’t require an instance of the class. They are a powerful tool in Python and can be used to simplify code and improve readability.