Ch 2File Handling in Python — Class 12 Computer Science, concept-first.

A program’s variables exist only while the program runs. Once execution ends, the data stored in those variables is lost.

Every file on a computer — whether it is a text document, an image, a video, or a program — is stored as a collection of 0s and 1s. That is the only language a computer understands.

A text file is simply a sequence of characters — alphabets, digits, and special symbols — stored permanently on a disk. Common examples include files with extensions like .txt, .py, and .csv.

Binary files store data as a sequence of bytes (0s and 1s), just like text files. The critical difference is what those bytes represent.

In real-world applications, programs work with data arriving from many different sources — databases, CSV files, HTML, XML, JSON feeds, and more.

To work with a file in Python, the first step is to open it. You do this using the open() function, which returns a file object (also called a file handle).

Once a file has been opened and you have finished reading from it or writing to it, you must close it.

The with clause in Python provides a cleaner and safer way to work with files. Its real power is that it handles file closing automatically — you never have to remember to call close().

To write data into a file, you must first open it in either write mode ('w') or append mode ('a'). If you open an existing file in write mode, its previous contents are erased and the file object is p…

The write() method is how you actually put data into a text file. It does not create a file — that is the job of the open() function with the 'w' mode.

The writelines() method is designed for writing multiple strings to a file in one go. Instead of calling write() repeatedly for each string, you pass an iterable object — like a list or a tuple — that…

Before you can read from a file, you must make sure it is opened in a mode that permits reading — "r", "r+", "w+", or "a+".

The read() method is how you pull data out of a file and into your Python program. It reads a specified number of bytes (characters) from the file, starting from the current position of the file point…

The readline() method reads exactly one line from a file. A "line" in a text file is any sequence of characters that ends with a newline character (n).

The readlines() method reads all the lines of a file at once and returns them as a list of strings. Each string in the list corresponds to one line from the file, and crucially, each string includes t…

The functions you have learnt so far — read(), readline(), readlines(), write(), writelines() — all access data sequentially: the file pointer moves forward as you read or write, and you cannot easily…

The tell() method answers a simple question: "Where exactly am I in this file right now?" When you read from or write to a file, the file object keeps track of its current position — like a cursor tha…

The seek() method lets you move the file object to a specific byte position inside a file. This is essential when you need to read from or write to a particular location without going through the enti…

Having learnt how to open and close a file, read and write data in a text file, and find or move the file object's position, let's now put these skills together to perform two basic operations on a te…

To create a file in Python, you use the open() method. This method takes two essential arguments: the filename and the mode in which you want to open it.

To read data back from a text file, you must open it in read mode ("r"). Once opened, reading begins from the very first byte of the file — the file pointer is at position 0.

Python treats everything as an object — lists, tuples, dictionaries, and even custom data structures are all objects.

The dump() method is how you write Python objects into a binary file — a process called pickling. Pickling converts a Python object (like a list, dictionary, or number) into a byte stream that can be…

The load() method is the counterpart of dump() — it brings data back from a binary file into a Python object. This process is called unpickling.

When you write data to a text file, everything becomes a string. Numbers, lists, dictionaries — all get converted to text.

- A file is a named location on a secondary storage media where data are permanently stored for later access.

Questions from official CBSE sample papers.