How to write large text files in Python

To write large text files in Python

To write large text files in Python , you can use the open() function with mode ‘w’ to open a file for writing. This function returns a file object that you can call the write() method on to write text to the file. Here’s an example:

with open('large_file.txt', 'w') as f:
    for i in range(1000000): # write 1 million lines
        f.write('Line {}\n'.format(i+1))

This code creates a file called ‘large_file.txt’ and writes 1 million lines to it, each containing a string and a line break. Note that using the ‘with’ statement ensures that the file is properly closed after writing, even if an exception is raised during the writing process.

If you need to write a large amount of data to a single line in the file, you can use the writelines() method instead of the write() method. This method takes an iterable of strings as its argument and writes each string to the file consecutively.

Keep in mind that writing very large files can be memory-intensive and slow, so you may need to consider alternative approaches such as writing data in chunks or using file compression techniques.

To read a large text file in Python

To read a large text file in Python, you can use the open() function with mode ‘r’ to open the file for reading. You can then use the read() method to read the entire contents of the file, or the readline() method to read each line of the file one at a time. However, if the file is very large, you may run into memory issues if you try to read the entire contents of the file into memory at once. In that case, you may want to consider reading the file in smaller chunks.

Here’s an example of how to read a large text file using the readline() method:

with open('large_file.txt', 'r') as f:
    line = f.readline()
    while line:
        # process the line
        line = f.readline()

This code reads each line of the file ‘large_file.txt’ and processes it one at a time, using a while loop to continue reading lines until the end of the file is reached.

Alternatively, you can use a for loop to read and process each line of the file like this:

with open('large_file.txt', 'r') as f:
    for line in f:
        pass
        # process the line

This will automatically iterate over each line in the file without having to manually call readline().

Keep in mind that reading very large files can be memory-intensive and slow, so you may need to consider alternative approaches such as processing the file in chunks or using file compression techniques.