Use input() in nltk.chat.chatbot() for Jupyter support

[tomaarsen]

Fixes #3021

Hello!

Pull request overview

• Replace sys.stdin.readline() with input() in nltk.chat.chatbot()

Details

The following snippet is used to let users pick which of the 5 NLTK chatbots should be instantiated:

nltk/nltk/chat/__init__.py

Lines 43 to 44 in 1f28903

	print("\nEnter a number in the range 1-%d: " % botcount, end=" ")
	choice = sys.stdin.readline().strip()

However, the sys.stdin.readline() constantly triggers in such a way that choice is an empty string. This causes an endless loop, exactly as described in #3021:

Note that this is the output directly after running the cell. Be warned when testing this, this ended up crashing my computer due to the endless loop.

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Changes

This PR simply updates this somewhat outdated form of getting user input by using the better supported input(). Running the cell now results in:

After which the chatbot works like intended & expected.

Thank you @jmcelroy01 for raising this issue.

• Tom Aarsen

[stevenbird]

Thanks @tomaarsen