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What is a text file?
That may seem a strange question: 

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a text file holds text – that's obvious.
But what does "text" mean? 

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A good definition is that a 
text file is "human readable". 

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You can open a text file in an editor – maybe 
notepad, on Windows, or TextEdit, on a Mac – 

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and you'll be able to read the contents.
All our Python .py files are text files. 

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We can read the contents in our IDE's editor.
A text file might also store HTML – 

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the contents that are displayed by 
your browser, when you visit a website. 

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For example, this is a very simple HTML document. 

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It might not make much sense, unless 
you understand HTML, but it is readable. 

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Storing data in text files is very convenient, 
because text files are easy to edit. 

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If we wanted to change the title, in the HTML 
document on the previous slide, we can open it 

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in our editor, make the change, and save the file.
Binary file formats are much harder to work with. 

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For example, editing video files requires 
special software – which can cost hundreds, 

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or thousands, of dollars.
Editing audio files also needs 

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you to install audio editing software, such as 
Audacity (which I mention because it's free). 

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Binary file formats are much harder to work with, 

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and you have to understand the 
binary format that was used, 

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before you can make sense of the contents.
Text files can be opened in any text editor. 

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Text files can be used to store plain text. 
The first text file that we'll work with, 

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in the next video, will contain the text of a poem.
But text files can also be used to store data. 

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There are many ways to store 
data in text files, including: 

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JSON – a data format derived from Javascript. 

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XML (and similar formats such as SSML).
CSV – Comma Separated Values. 

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Pickle files – a Python-specific 
way to serialise data. 

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We won't look at XML in this section, but we 
will be seeing examples of JSON and CSV files. 

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And, because this is a Python course, 
we'll be looking at Python's pickle format. 

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We'll get started by reading and writing 
plain text files. See you in the next video.