Readlines

Q: How deeply does A Pythonic Adventure: From Python basics to a working web app cover readlines?

Shows the return type, newline characters, and a loop-based cleanup pattern, but not lower-level file internals.

As explained in A Pythonic Adventure: From Python basics to a working web app

The Python file readlines method returns the lines read from a file as a list of strings.

Use readlines() when a file’s contents need to become a list instead of one large string. Each list item represents one line and usually includes its newline character. section 5.0

Read a drink menu

For a file containing coffee, chocolate, and decaf, f.readlines() produces ['coffee\n', 'chocolate\n', 'decaf\n']. Check type(drinks) to see that the result is a list. To remove the newline characters, loop over the items and apply strip(). section 5.0

f = open("drinks.txt")
drinks = f.readlines()
print(drinks)

Compare the readlines() call with its printed list result and type check. section 5.0

A practical file-reading pattern is:

Call readlines() on an opened file. section 5.0
Loop through the returned lines, strip each item, and append the cleaned value to a new list. section 5.0

How A Pythonic Adventure: From Python basics to a working web app covers it

Cover of A Pythonic Adventure: From Python basics to a working web app

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Also explained in

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The Quick Python Book, Fourth Editionreadlines is a file-object method that reads all remaining lines from an open stream and returns them as a list.

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Related concepts

listproduces · A list is an ordered collection of elements arranged in a sequence.
list()produces · list() is Python’s built-in constructor that creates a new list from an iterable, or an empty list when called without arguments.
writelinesequivalent to · writelines is a file-object method that writes strings from an iterable consecutively without automatically adding newline characters.
read operationalternative to · A read operation retrieves data from a source, typically without changing the underlying data being read.
readlinealternative to · Readline is an operation or API that reads the next line or line fragment from an input stream or file-like source.

This explainer was generated by Manning's knowledge graph from the text of A Pythonic Adventure: From Python basics to a working web app. The section links point to the parts of the book it draws on.