Question

how does a file reader know where one line starts and another ends?
the last item in a line of data does not have a comma after it.
every line in a text file has a hidden eol (end of line) set of characters.
every line starts with a bol (beginning of line) character.
python knows how many characters to expect in a line.

Explanation:

In text files, each line has an end - of - line (EOL) character or sequence (like '
' in Unix - like systems or '
' in Windows). File readers use these hidden EOL characters to identify line boundaries. The absence of a comma at the end of a line is not a standard way to mark line endings. There is no universal BOL character that is used in the same way as EOL for identifying lines. And Python doesn't inherently know how many characters are in a line without reading the EOL characters.

Answer:

Every line in a text file has a hidden EOL (end of line) set of characters.