Reading an External File

Lesson partially adapted from “Python File Handling: How to Create Text File, Read, Write, Open, Append Files in Python.” Guru99, www.guru99.com/reading-and-writing-files-in-python.html.

Python is capable of reading and writing to files without importing any libraries. However, working with files in Python is slightly different from working with programs like Microsoft Word or Excel.

In Windows, for example, a file can be any item manipulated, edited or created by the user/OS. That means files can be images, text documents, executables, and much more. Most files are organized by keeping them in individual folders. In Python, a file is categorized as either text or binary, and the difference between the two file types is important. Text files are structured as a sequence of lines, where each line includes a sequence of characters. This is what you know as code or syntax.
(“Reading and Writing Files in Python.” Python For Beginners, www.pythonforbeginners.com/files/reading-and-writing-files-in-python.)

Opening Files

Text files are the easiest to change in Python. But before a file can be edited, you must open it. In order to open a file for writing or use in Python, you must rely on the built-in open () function. The argument of the open function is the path to the file. If the file is in the current working directory of the program, you can specify only its name. An argument is nothing more than a value that has been provided to a function, which is relayed when you call it. So, for instance, if we declare the name of a file as “filename.txt,” that name would be considered an argument.

Syntax of Python open file function

file_object = open("filename", "mode")

Here,

• filename: gives name of the file that the file object has opened.
• mode: attribute of a file object tells you which mode a file was opened in.

By adding a second argument to the open function, we can specify the mode:

• "r" means open in read mode, which is the default.
• "w" means write mode, for rewriting the contents of a file.
• "a" means append mode, for adding new content to the end of the file.
• “b” means open in binary mode, for non-text files such as images. Binary mode must be added to another one of the above modes.

Let's look at the old way of opening and reading files:

Using a with statement eliminates the need to close the file. Let's look at an example of opening and reading a file using a with statement:

So far we have just looked at examples of reading text files. For more information on using CSV files, visit the link below:
Reading CSV files in Python