How to Read Text Files into Python Lists or Arrays: A Comprehensive Guide

Reading Text Files into Python Lists or Arrays

In Python, accessing individual items from a file's contents is essential for data manipulation. To achieve this, understanding how to read a text file into a list or an array is crucial.

Consider the following scenario: You have a text file with a comma-separated list of values, and you want to load these values into a list or array for easy manipulation.

Using the code snippet:

<code class="python">text_file = open("filename.dat", "r")
lines = text_file.readlines()
print(lines)
print(len(lines))
text_file.close()</code>

You may notice that the entire file content is loaded into a single element in the list. To rectify this, you need to split the string into individual values using the split() function.

<code class="python">text_file = open("filename.dat", "r")
lines = text_file.read().split(',')
text_file.close()</code>

Now, lines will be a list of individual values from the text file. You can access each item using index notation, such as lines[0] for the first value.

Additionally, you can use the csv module to read the file as a comma-separated value (CSV) file. This provides a more idiomatic approach:

<code class="python">import csv

with open('filename.csv', 'r') as fd:
    reader = csv.reader(fd)
    for row in reader:
        # do something with each row</code>

By employing these techniques, you can effectively read text files into Python lists or arrays, giving you the flexibility to manipulate data and perform any necessary operations.

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