29_writing_clean_functions.py

#======================================================================================
#                                 Bad Style
#======================================================================================

def DiscPrint(p, r):
    print('Calculating discount')
    p = p - (p * r/100)
    print(p)

DiscPrint(80, 20)

#======================================================================================
# write functions that are easy to read and understand(for you and others!)
#======================================================================================

#--------------------------------------------------------------------------------------
# Rule:1 Use snake_case for Function Names
#--------------------------------------------------------------------------------------
# write function names in lowercase and separate words with underscores
# ex:load_data_from_file
#--------------------------------------------------------------------------------------


#--------------------------------------------------------------------------------------
# Rule2: Use Clear Descriptive Function Names
#--------------------------------------------------------------------------------------
# Describe exactly what the function does
# Start with a verb
# Use full words, avoid abbreviations
#--------------------------------------------------------------------------------------


#--------------------------------------------------------------------------------------
# Rule3: Parameters Names Describe Their Values
#--------------------------------------------------------------------------------------
# Use full, meaning words
# Avoid abbreviations and single letters
# ex: "price", 'country_code"
#--------------------------------------------------------------------------------------


#--------------------------------------------------------------------------------------
# Rule4: Always Describe Functions using Docstring
#--------------------------------------------------------------------------------------
# A docstring is a description of a function written inside triple quotes(""" """).
# Help teammates understand your code
# Help future you remember the logic
#--------------------------------------------------------------------------------------


#--------------------------------------------------------------------------------------
# Why not use comments instead of docstring?
#--------------------------------------------------------------------------------------
# comment #(python ignores comment, they are only notes for us)
# Docstring""" """(python stores it inside the function and can be reused by tools, editors..)
#--------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------

# Rule5: Replace Prints with Return to send data back to program
#--------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------
# Rule6: Don't change parameter values directly, create local variables for any processing.
#--------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------
# Rule7: Use Data Type Hints
# Always add type hints to parameters and return to make the function easier to understand
#--------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------
# Rule8: Explain Args and Return in Docstring
#--------------------------------------------------------------------------------------
# Always describe what goes in and what comes out of the function in the docstring
#--------------------------------------------------------------------------------------

#======================================================================================
#                               Good Style
#======================================================================================

def calculate_discount(price:float, rate:float)->float:
    """
    Calculate the final price after applying a discount.
    Args:
        price (float): Original Product Price.
        rate (float): Discount Rate as numbers(e.g 20 for 20%)
    Returns:
        final_price (float): Final Price after applying discount.
    """
    final_price = price - (price * rate/100)
    return final_price

calculate_discount(100,20)