Python Files I/O

Python provides a simple and easy-to-use interface for working with files. The built-in open() function can be used to open and manipulate files, and the os and os.path modules provide additional functionality for working with the file system.

When working with files, it’s important to keep in mind that a file must be opened before it can be read or written to, and that a file should be closed after it’s no longer needed. The open() function is used to open a file, and it returns a file object that can be used to read or write to the file.

The open() function in python takes in two arguments: the name of the file to be opened and the mode in which to open the file. The mode can be either  ‘r’ for reading, ‘w’ for writing, or ‘a’ for appending.

When reading a file, Python provides several methods such as file.read(), file.readline() and file.readlines() to read the contents of the file. The file.read() method reads the entire content of the file, file.readline() reads the next line of the entire file and file.readlines() reads all the lines of the entire file and returns them as a list of strings.

When writing to a file, Python provides the file.write() and file.writelines() methods. The file.write() method writes a single string to the file, and the file.writelines() method writes a list of strings to the provided file.

It’s generally a good practice to close the file after you’re done with it, to free up system resources. One can also use the command with statement to open and close the file, so that the file is automatically closed after all the code is indentened beneath it.

Python File I/O methods

Python provides several built-in methods for working with files. Some of the most commonly used methods are:

1. open(filename, mode):

Opens a file with the given filename and mode (‘r’ for reading, ‘w’ for writing, ‘a’ for appending). Returns a file object.

Example:

Opening a file for reading:

f = open('example.txt', 'r')
print(f.read())
f.close()

Output:

Opening a file for writing:

f = open('example.txt', 'r')
print(f.read())
f.close()

2. file.read([size]):

Reads at most size bytes from the provided file. If size is not specified, it reads the entire file.3

Example:

f = open('example.txt', 'r')
print(f.read())
f.close()

3. file.readline():

Reads the next line of the provided file.

Example:

f = open('example.txt', 'r')
print(f.readline()) # prints the first line of the file
print(f.readline()) # prints the second line of the file
f.close()

Output:

4. file.readlines():

Returns a list of all the lines in the given file.

Example:

f = open('example.txt', 'r')
lines = f.readlines()
print(lines)
f.close()

Output:

5. file.write(string):

Writes the string to the file.

Example:

f = open('example.txt', 'w')
f.write('Hello, World!')
f.close()

6. file.writelines(lines):

Writes a list of lines to the given file.

Example:

f = open('example.txt', 'w')
f.write('Hello, World!')
f.close()

Output:

7. file.seek(offset[, whence]):

Changes the file position to the given offset. The whence argument is one of the optional arguments  and defaults to 0 (absolute file positioning); other values are 1 (seek relative to the current position) and 2 (seek relative to the file’s end).

Example:

f = open('example.txt', 'r')
print(f.read(5)) # prints the first 5 characters of the file
f.seek(5) # moves the pointer to the 6th character
print(f.read()) # prints the rest of the file
f.close()

Output

8. file.tell():

Returns the current file position.

Example:

f = open('example.txt', 'r')
print(f.read(5)) # prints the first 5 characters of the file
print("current position:", f.tell()) # prints the current position of the pointer
f.seek(5) # moves the pointer to the 6th character
print(f.read()) # prints the rest of the file
f.close()

Output:

9. file.close(): Closes the file.

Example:

f = open('example.txt', 'r')
print(f.read())
f.close()

Output:

Python also provides the os and os.path modules for working with the file system, including creating, deleting, and renaming files and directories.

Python os module

The os module in Python provides several methods for working with the file system. Some of the commonly used file I/O methods are:

1. os.rename(src, dst): Renames the file or directory at the path ‘src’ to the path ‘dst’.

2. os.remove(path): Removes the file at the specified path.

3. os.mkdir(path[, mode]): Creates a new directory at the specified path, with the specified permissions (mode).

4. os.rmdir(path): Removes the directory at the specified path.

5. os.chdir(path): Changes the current working directory to the path which is specified

6. os.getcwd(): Returns the current working directory.

7. os.listdir(path): Returns a list of files and directories in the specified directory.

8. os.path.exists(path): Returns True if the specified path exists, False otherwise.

9. os.path.isfile(path): Returns True if the specified path is a file, False otherwise.

10. os.path.isdir(path): Returns True if the specified path is a directory, False otherwise.

It’s worth noting that these methods can raise an OSError exception if something goes wrong. For example, if the specified file or directory does not exist or if the user  decides not to have the necessary permissions to perform the operation.

In addition, the os.path module provides several useful methods for working with file paths, for example os.path.join() for joining paths, os.path.split() for splitting a path into its component parts, and os.path.abspath() for getting the absolute path of a file.

os.path module in Python

The os.path module in Python provides several methods for working with file paths. Some of the commonly used file I/O methods are:

1. os.path.join(path1, path2): Joins two paths together and returns the resulting path. This is useful for creating platform-independent paths.

2. os.path.split(path): Splits the specified path into a tuple containing the head (all but the last part of the path) and the tail (the last part of the path).

3. os.path.basename(path): Returns the base name of the specified path, that is, the last part of the path.

4. os.path.dirname(path): Returns the directory name of the specified path, that is, all but the last part of the path.

5. os.path.abspath(path): Returns the absolute path of the specified path.

6. os.path.normpath(path): Returns the normalized path, that is, it collapses redundant separators and removes “.” and “..” components.

7. os.path.splitext(path): Returns a tuple containing the root and the extension of the specified path.

8. os.path.expanduser(path): The commands expand the given path to include the user’s home directory if the path starts with “~”.

9. os.path.getsize(path): Returns the size of the specified file in bytes.

10. os.path.getatime(path): Returns the time of the last access of the specified file.

These methods can be used to extract different parts of a file path, check if a file or directory exists, check for the type of file or directory, and perform other operations on file paths without having to work with the file directly.

Conclusion

We can say that  Python provides a simple and easy-to-use interface for working with files. The built-in open() function can be used to open and manipulate files, and the os and os.path modules provide additional functionality for working with the file system.

It’s generally a good practice to close the file after you’re done with it, to free up system resources. One can also use the with a statement to open and close the given file so that the file is automatically closed after all the indented code beneath it is executed.

In this way, one can handle files very efficiently in python, reading and writing data to files as per our requirements and also managing the file pointers and system resources.