One-liner Python code for setting string to 0 string if empty

Question

What is a one-liner code for setting a string in python to the string, 0 if the string is empty?

# line_parts[0] can be empty
# if so, set a to the string, 0
# one-liner solution should be part of the following line of code if possible
a = line_parts[0] ...

Do you mean string is empty(means string of length zero) or None ? — Manish Sinha
– Manish Sinha, Commented Aug 31, 2009 at 11:09

Ned Batchelder · Accepted Answer · 2009-08-27 02:16:41Z

90

a = line_parts[0] or "0"

This is one of the nicest Python idioms, making it easy to provide default values. It's often used like this for default values of functions:

def fn(arg1, arg2=None):
    arg2 = arg2 or ["weird default value"]

answered Aug 27, 2009 at 2:16

Ned Batchelder

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3 Comments

Mark Rushakoff Over a year ago

To clarify, if it wasn't clear from Ned's answer: when it comes to strings, an empty string always evaluates to False, and a non-empty string always evaluates to True -- that's why or works perfectly in this situation.

legesh Over a year ago

I don't understand - what the difference then to give a default value in a definition of a function: def fn(arg1, arg2="weird default value"): ?

Ned Batchelder Over a year ago

You can do that, but have to be careful with mutable defaults, or defaults based on changing data that may not be available at definition time.

Andrew Keeton · Accepted Answer · 2009-08-27 02:15:50Z

13

a = '0' if not line_parts[0] else line_parts[0]

answered Aug 27, 2009 at 2:15

Andrew Keeton

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1 Comment

recursive Over a year ago

Would be more clear as: a = line_parts[0] if line_parts[0] else '0'

Kannan Ramamoorthy · Accepted Answer · 2018-09-27 08:12:07Z

0

If you would also like to consider the white spaces as empty and get the result stripping of those, the below code will help,

a = (line_parts[0] and line_parts[0].strip()) or "0"

answered Sep 27, 2018 at 8:12

Kannan Ramamoorthy

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