Q.(a) Write a Python function that counts and returns the number of digits appearing in the text file "Space.txt". For example, if the file contains : Space exploration has unlocked incredible advancements in technology and science. Since the first moon landing in 1969, space agencies have sent probes to Mars, Jupiter and beyond. The ISS, orbiting Earth at about 400 km, serves as a hub for research. With missions planned for 2030, humanity’s cosmic journey continues! Then the function should return 11.

File Handling Methods: A First Look

Think about the last time you saved a document on your computer. You clicked "Save," gave it a name, and later opened it again to continue working. That simple act—storing information so you can retrieve it later—is the entire reason file handling exists. Every time you work with a file, whether it's a Word document, a PDF, or even a photo, you are performing file handling.

At its core, file handling is the process of creating, reading, updating, and deleting files through a computer program. It is how a program talks to the storage on your machine—the hard drive or SSD—rather than just working with data that disappears when you close the program.

The Two Fundamental Modes

When a program wants to work with a file, it must first open that file. Opening a file is like unlocking a drawer: you decide what you want to do with it before you start. There are two basic intentions:

• Reading – You want to look at the contents of the file without changing anything. The file stays exactly as it is.
• Writing – You want to put new content into the file, either by starting fresh (overwriting everything) or by adding to what is already there (appending).

These two intentions define the mode in which you open the file. A file opened for reading cannot be written to, and a file opened for writing cannot be read from—at least not in the simplest approach. This separation exists to prevent accidents: you do not want a program that is supposed to only display your data to accidentally erase it.

The Lifecycle of a File Operation

Every file handling operation follows a fixed sequence. You cannot skip a step without causing trouble.

1. Open the file – You tell the program which file you want and what you intend to do with it (read or write). The program checks whether the file exists (for reading) or whether it can create a new one (for writing).
2. Perform the operation – You either read the data from the file into your program's memory, or you write data from your program into the file. This step can happen many times—you might read one line, then another, then another.
3. Close the file – You tell the program you are done. This step is crucial. Closing a file saves any changes you made and frees up the file so other programs can use it.

Why This Matters for a Commerce or Humanities Student

You might wonder why a student of commerce or humanities needs to understand file handling. The answer is simple: almost every modern business, government office, and research project deals with data stored in files.

• A commerce student analyzing sales records will need to read data from a spreadsheet file, process it, and write the results to a new file.
• A humanities student working with historical documents might need to read text files containing old letters, clean up the formatting, and save the cleaned version.
• Anyone managing a database or a website will encounter file handling when uploading images, generating reports, or backing up information. …

File Input Output Filtering

Think of a water filter. You pour in tap water, and what comes out is cleaner, purer, and ready to drink. The filter doesn't create new water — it takes what's already there and transforms it by removing impurities or adding something useful.

File Input Output Filtering works on the same principle. It is a way of processing data as it moves from one place to another — typically from an input source (like a file or keyboard) to an output destination (like a file or screen). The "filter" sits in between, reading the incoming data, modifying it in some way, and then writing the modified version out.

The Core Idea

At its simplest, a filter takes a stream of data, performs a transformation on it, and produces a new stream. The transformation could be anything: converting all letters to uppercase, removing blank lines, replacing one word with another, or rearranging the order of records.

The key insight is that the filter does not care where the data came from or where it is going. It only cares about what to do with the data as it passes through. This makes filters reusable — the same filter can work on data from a file, from a user typing at a keyboard, or from the output of another program.

Why It Matters

In the real world, data rarely arrives in the exact format you need. A bank might receive transaction records with dates written as "2024-03-15" but their system expects "15 March 2024". A school might get student lists with names in lowercase but needs them capitalised. A business might export a report with extra blank lines that clutter the final document.

Instead of rewriting entire programs for each of these situations, you can use filters. You take the raw data, run it through the appropriate filter, and get exactly what you need on the other side.

How It Works in Practice

A filter typically follows a simple pattern:

• Read one piece of data (a line, a character, a record)
• Process it according to the rule
• Write the result
• Repeat until there is no more data

This is called a "loop" — the filter keeps doing the same thing over and over until the input runs out. Because it processes data piece by piece rather than loading everything into memory at once, it can handle enormous files without slowing down.

Common Types of Filters

Filters can be grouped by what they do to the data:

Transformation filters change the content itself. Converting text to uppercase, replacing British spellings with American ones, or encrypting sensitive information are all transformations.

Selection filters choose which pieces of data to keep and which to discard. A filter that removes all lines containing the word "ERROR" is a selection filter — it lets some data through and blocks the rest.

Formatting filters change the appearance or structure without altering the meaning. Adding line numbers to a document, aligning columns, or inserting page breaks are formatting operations.

Combination filters do more than one thing. A filter might remove blank lines, convert everything to lowercase, and then add a timestamp to each line — all in a single pass.

The Chain Concept

The real power of filtering emerges when you connect filters together. The output of one filter becomes the input to the next. This is called a "pipeline" or "chain."

Imagine you have a raw data file with messy entries. You could:

1. First filter: remove blank lines
2. Second filter: convert all text to uppercase
3. Third filter: sort the lines alphabetically
4. Fourth filter: add line numbers

Each filter does one simple job. Together, they produce a clean, numbered, sorted, uppercase document from the original mess. You can rearrange, add, or remove filters without changing any of them individually.

A Concrete Example Without Numbers …