22 File Handling in Python Interview Questions and Answers

Python is a versatile language that is widely used in many different industries. One of the reasons for its popularity is its ability to handle files. When applying for a Python-related position, it is likely that you will be asked questions about file handling. Knowing how to answer these questions can help you stand out from the other candidates and land the job. In this article, we will discuss some of the most common file handling questions and how you should answer them.

File Handling in Python Interview Questions and Answers

Here are 22 commonly asked File Handling in Python interview questions and answers to prepare you for your interview:

1. What is file handling in Python?

File handling is the process of reading, writing, and manipulating files in Python. This can be done with the built-in open() function, which takes two arguments: the path to the file and the mode in which to open it. The mode argument specifies how the file should be opened, and can be ‘r’ for reading, ‘w’ for writing, or ‘a’ for appending.

2. Can you explain the different modes of opening a file in Python?

There are three different modes of opening a file in Python: read mode, write mode, and append mode. Read mode is the default mode and allows you to read the contents of a file. Write mode will allow you to write to a file, and append mode will allow you to add new data to the end of an existing file.

3. How do you create a text file using Python?

You can create a text file using Python by opening a new file in write mode. This will allow you to write data to the file.

4. How do you read and write to an existing file in Python?

To read an existing file in Python, you can use the built-in open() function. This function takes two arguments: the name of the file to read, and the mode in which to open the file. The mode argument is optional, but it allows you to specify how you want to interact with the file. The most common mode is ‘r’, which stands for read-only. To write to an existing file, you can use the same open() function, but you must specify the ‘w’ mode argument. This will allow you to write to the file.

5. Is it possible to open multiple files using Python? If yes, then how?

Yes, it is possible to open multiple files using Python. You can do this by using the built-in open() function. When you call open(), you can specify the mode in which you want to open the file, as well as the name of the file. If you want to open multiple files, you can do so by passing a list of filenames to open().

6. How should you handle exceptions when dealing with files in Python?

When working with files in Python, it is important to be aware of potential exceptions that could be raised. Some common exceptions include IOError, which is raised when there is an error reading or writing to a file, and ValueError, which is raised when there is an issue with the format of the data in the file. It is important to handle these exceptions appropriately in order to avoid potential data loss or corruption.

7. What are some important methods used for reading from a file in Python?

Some important methods used for reading from a file in Python are the read() and readline() methods. The read() method reads the entire contents of a file into a string, while the readline() method reads a single line from a file.

8. What are some common errors that can occur while working with files in Python?

Some common errors that can occur while working with files in Python include trying to open a file that does not exist, or trying to read from a file that has not been opened. Other errors can occur if you try to write to a file that is read-only, or if you try to close a file that is already closed.

9. What’s the difference between binary and text files in Python?

Binary files are files that are not meant to be read by humans – they are meant to be read by computers. Binary files are typically faster to read and write than text files because the computer can read the entire file in one go, without having to stop to process the data. Text files, on the other hand, are meant to be read by humans. They are typically slower to read and write than binary files because the computer has to stop to process the data.

10. Why is it not recommended to use pickle or cPickle modules for serializing objects into a file?

The pickle and cPickle modules are not recommended for use because they are insecure. Because these modules can execute arbitrary code, they could be used by an attacker to compromise the security of your system.

11. Which functions allow us to check if we have reached the end of a file in Python?

The functions that allow us to check if we have reached the end of a file in Python are the eof() and tell() functions. The eof() function returns true if we have reached the end of the file, and the tell() function returns the current position of the file pointer.

12. When trying to open a file in Python, I get the error “FileNotFoundError: [Errno 2] No such file or directory”. What could be the cause of this issue?

There are a few potential causes for this error. The first is that the file you are trying to open does not actually exist in the directory you are looking in. The second is that you do not have permission to access the file. The third is that the file is already open by another process.

13. How can you convert a CSV file to a dataframe in Pandas?

You can use the read_csv() function in Pandas to convert a CSV file to a dataframe.

14. How can you sort a list of strings alphabetically without using sorted()?

You can use the “sort” method.

15. List down the steps involved in processing a large file in Python?

There are a few steps involved in processing a large file in Python:

1. Open the file using the open() function.
2. Read in the file using either the read() or readline() function.
3. Process the data in the file as needed.
4. Close the file using the close() function.

16. What does the following code snippet do?

The following code snippet opens the file “myfile.txt” for reading, and then reads in the contents of the file line by line, printing each line out as it goes.

17. a = open(“file”, ‘w’)

The open() function opens the file in write mode. The ‘w’ character stands for write. The file will be created if it doesn’t exist. If it exists, the data in the file will be overwritten.

18. a.write(‘Hello World’)

This code will write the string ‘Hello World’ to the file ‘a’.

19. What is the best way to extract all lines that start with a particular letter?

One way to do this would be to use the Python built-in open() function to open the file, then use the for loop to iterate through each line in the file. For each line, you can use the Python startswith() method to check if the line starts with the desired letter. If it does, you can add it to a list or print it out.

20. What are some examples of sequence types in Python?

Some examples of sequence types in Python include lists, tuples, and strings.

21. What is the usage of yield keyword in Python?

The yield keyword is used in Python to define generators. Generators are a special type of function that allow the programmer to return values one at a time, rather than returning all values at once. This can be useful when working with large data sets, as it allows the programmer to process the data one piece at a time, rather than having to load the entire data set into memory at once.

22. What is the purpose of enumerate() function in Python?

The enumerate() function is used to iterate over a list of items, while keeping track of the index of each item in the list. This can be useful when you need to know not only the contents of the list, but also where each item is located in the list.