Q.Consider the statement given below : f1 = open("pqr.dat","________") Which of the following is the correct file mode to open the file in read only mode ? (A) a (B) rb (C) r+ (D) rb+

When you work with files in Python, the mode string you pass to the open() function determines exactly what you can do with that file — read, write, append, or a combination. The question asks specifically for read-only mode, which means the file should be opened only for reading, not for writing or appending.

Let's look at each option:

• (A) "a" — This stands for append mode. It opens the file for writing, but data is added at the end of the file. It is not read-only at all. In fact, if the file does not exist, "a" creates a new one. So this is incorrect.

• (B) "rb" — The "r" means read, and the "b" means binary mode. Together, "rb" opens the file for reading in binary format. This is indeed a read-only mode — you cannot write to the file. Among the given options, this is the correct one.

• (C) "r+" — The "+" adds both reading and writing. So "r+" opens the file for both reading and writing. It is not read-only; you can modify the file. Hence, it is incorrect for the given requirement.

• (D) "rb+" — This combines binary mode with read-write access. Like "r+", it allows both reading and writing, just in binary format. So it is also not read-only. …

When working with files in programming, the mode you choose determines not just whether you can read or write, but also where the file pointer starts and how the existing content is treated. Understanding these distinctions is essential for handling data correctly.

The r mode opens a file for reading only. The file pointer sits at the beginning, ready to read from the start. You cannot write in this mode, and if the file doesn't exist, you'll get an error. It's purely for consumption of existing data.

The r+ mode opens a file for both reading and writing. The file pointer again starts at the beginning. This means if you write immediately, you'll overwrite existing content from the start unless you explicitly move the pointer. The file must already exist, or the operation fails. It's a two-way mode but begins at the top.

The w mode opens a file for writing. Here's the crucial behavior: it truncates the file, meaning any existing content is wiped out the moment you open it. The file pointer is at the beginning of what is now an empty (or newly created) file. If the file didn't exist, it gets created. This mode is destructive by design. …

When working with files in Python, we often need to specify how we intend to interact with the file. This is done through what are called "modes" when opening a file. These modes dictate whether you want to read from the file, write to it, append new content, or a combination of these actions, and also define how the system should behave if the file doesn't exist or already contains data. Understanding these modes is fundamental to effective file handling.

Let's look at the common file modes:

• 'r' (Read Mode):

  This is the default mode. When you open a file in read mode, you can only read its contents. You cannot modify or add new data.

  Watch out

  If the file you are trying to open in 'r' mode does not exist, Python will raise a FileNotFoundError. It will never create a new file in this mode.

• 'r+' (Read and Write Mode):

  This mode allows you to both read from and write to a file. The file pointer is initially at the beginning of the file.

  Important

  Similar to 'r' mode, if the file does not exist when opened in 'r+' mode, Python will raise a FileNotFoundError. It does not create a new file. If the file exists, writing will occur from the current position of the file pointer, potentially overwriting existing content from that point onwards.

• 'w' (Write Mode):

  This mode is specifically for writing data to a file. It has a very distinct behavior regarding file existence:

  • If the file does not exist, Python will create a new, empty file with the specified name. …

Part (a)

To write new content into a text file you use write mode, "w". If the file does not exist Python creates it; if it does exist, its contents are truncated (erased) before writing begins.

f = open("WRITEUP.TXT", "w")
``` …