Question

The purpose of this exercise is to make a program which takes a date, consisting of year (4 digits), month (2 digits), and day (1-31) on the command line and prints the corresponding name of the weekday (Monday, Tuesday, etc.). Python has a module calendar, which you must look up in the Python Library Reference (see Chapter 2.6.3), for calculating the weekday of a date. Name of program file: weekday.py. \(\diamond\)

Short answer

Use the Python `calendar` module to convert a date to a weekday name and print it using command-line inputs.

Step-by-step solution

Import the Required Module

Begin your program by importing the `calendar` module in Python. This module contains necessary functions to calculate the day of the week from a given date. Use the import statement: `import calendar`.

Accept Command-Line Arguments

You will need the `sys` module to accept command-line inputs. Import it using `import sys`. Use `sys.argv` to capture the inputs, where `sys.argv[1]` is the year, `sys.argv[2]` is the month, and `sys.argv[3]` is the day.

Convert Inputs to Integer

Since command-line inputs are captured as strings, convert them to integers. For example, use `year = int(sys.argv[1])`, `month = int(sys.argv[2])`, and `day = int(sys.argv[3])`. This conversion is necessary for the `calendar` module functions.

Calculate the Weekday Number

Use the function `calendar.weekday(year, month, day)` to calculate the day of the week. This function returns an integer from 0 (Monday) to 6 (Sunday). Store the result in a variable: `weekday_number = calendar.weekday(year, month, day)`.

Convert Weekday Number to Name

The `calendar` module has a list `calendar.day_name` which maps numbers to weekday names. Use this list to convert `weekday_number` to a weekday name: `weekday_name = calendar.day_name[weekday_number]`.

Output the Weekday Name

Finally, print the weekday name with a statement such as `print('The day of the week is:', weekday_name)`. This will show the matching weekday name based on the provided date.

Key concepts

calendar module

In Python, the `calendar` module is a handy toolkit that helps you work with dates, calendars, and more. You can use it to find out what day of the week a specific date falls on, among other things. To access this module in your program, you simply need to include the line `import calendar`.

• This module gives us access to various useful classes and methods, such as `calendar.weekday(year, month, day)` which returns the day of the week for the given date.
• The days are represented as integers, where 0 is Monday and 6 is Sunday.
• Another valuable feature is the `calendar.day_name`, which lets you convert these integers into human-readable weekday names like 'Monday' or 'Tuesday'.

The `calendar` module is a great way to make date manipulation a breeze, providing all you need to handle dates smoothly in your scripts.

command-line arguments

Command-line arguments are a way to provide input to your Python program directly from the terminal or command prompt. This makes it convenient to run scripts with different inputs without changing the code. To use them, you'll need to import the `sys` module: `import sys`.

• The `sys.argv` list captures these arguments. It's a list where `sys.argv[0]` is the script name, and any following values are the arguments you provide.
• For instance, if you execute the script `weekday.py` with `python weekday.py 2023 10 25`, `sys.argv[1]` would be '2023', `sys.argv[2]` would be '10', and `sys.argv[3]` would be '25'.
• Remember, command-line arguments are strings, so if you need to perform arithmetic or other operations, you'll often need to convert them to integers or floats using `int()` or `float()`.

Command-line arguments provide a simple yet powerful way to interact with your Python scripts, making them dynamic and versatile for different scenarios.

weekday calculation

Calculating the day of the week for a given date is quite practical, and Python's `calendar` module provides a straightforward way to perform this calculation. After importing the module, you can calculate the weekday with the `calendar.weekday(year, month, day)` function.

• This function needs three integers as input: a year, a month, and a day.
• It returns an integer that represents the day of the week, with values ranging from 0 (Monday) to 6 (Sunday).
• Once you have this integer, you can easily convert it to a string using `calendar.day_name`, which helps you print the name of the weekday directly.

Thanks to Python's built-in functions, you can quickly find out what day of the week a specific date lands on, making your date-handling code concise and efficient.

Python Library Reference

The Python Library Reference is an essential resource for both novice and experienced programmers. It contains comprehensive documentation on all built-in modules and functions available in Python, including those in the `calendar` module. Accessing this resource can significantly enhance your coding skills.

• You can find descriptions and examples of how to use various modules and functions.
• For instance, the documentation for the `calendar` module explains how to work with dates and provides examples of its many features.
• Exploring the Python Library Reference can also introduce you to new modules that can simplify your programming tasks or solve problems more efficiently.

Regularly consulting the Python Library Reference will help you better understand the powerful tools at your disposal and inspire you to write more elegant and effective code.