Python Syntax for Assigning Multiple Variables Across Multiple Lines

Question

I'm am trying to assign values to multiple variables in one statement, but I cannot figure out if there is a nice syntax to split it across multiple lines.

# This is the long version I don't want
a, b, c, d = tf.constant(1, name='constant_a'), tf.constant(2, name='constant_b'), tf.constant(3, name='constant_c'), tf.constant(4, name='constant_d')

# Does something like this exist?
a, b, c, d = tf.constant(1, name='constant_a'), /
             tf.constant(2, name='constant_b'), /
             tf.constant(3, name='constant_c'), /
             tf.constant(4, name='constant_d')

Is there a nice, Pythonic way to do this?

What is your motivation for that? (except curiosity?) What is the problem with simply: python a = tf.constant(..) ... d = tf.constant(..) ? — pierresegonne
– pierresegonne, Commented Apr 13, 2020 at 14:22

wjandrea · Accepted Answer · 2020-04-13 15:01:57Z

1

I think you were thinking of backslash (line continuation).

a, b, c, d = tf.constant(1, name='constant_a'), \
             tf.constant(2, name='constant_b'), \
             tf.constant(3, name='constant_c'), \
             tf.constant(4, name='constant_d')

This works, but it's ugly. Better to use a tuple/list like in Joseph's answer, or better yet a comprehension like in Josh's answer.

edited Apr 13, 2020 at 15:01

answered Apr 13, 2020 at 14:48

wjandrea

33.8k10 gold badges69 silver badges105 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Alan Over a year ago

Yes I was! Thanks, I could have sworn that syntax existed but I couldn't figure out why it wouldn't work. I happen to agree it's ugly, I just wanted confirmation the line continuation syntax worked in assigning multiple variables. Silly mistake in the end, cheers for the answer!

wjandrea · Accepted Answer · 2020-04-13 14:24:34Z

1

Not sure if it's more readable/Pythonic, but this is the most succinct!

a, b, c, d = [tf.constant(i, name='constant_' + x) for i, x in zip(range(1, 5), 'abcd')]

edited Apr 13, 2020 at 14:24

wjandrea

33.8k10 gold badges69 silver badges105 bronze badges

answered Apr 13, 2020 at 14:23

Josh Friedlander

11.8k7 gold badges42 silver badges89 bronze badges

Comments

Joseph O'Donnell · Accepted Answer · 2020-04-13 16:01:26Z

1

Wrap what you have in parenthesis.

a, b, c, d = (tf.constant(1, name='constant_a'), 
              tf.constant(2, name='constant_b'), 
              tf.constant(3, name='constant_c'),
              tf.constant(4, name='constant_d'))

edited Apr 13, 2020 at 16:01

answered Apr 13, 2020 at 14:21

Joseph O'Donnell

214 bronze badges

4 Comments

wjandrea Over a year ago

might as well use square brackets since they stand out more from the parentheses of the function calls, and there's no real difference between a list and a tuple in this context. BTW welcome to SO!

Joseph O'Donnell Over a year ago

You're right that using square brackets looks a bit more Pythonic as it were. I chose the tuple because I found that it is ~1.3x faster than using a list in this context, although I need to think on why... The calculation time is so small for both it really doesn't matter though. Thanks for the welcome! I'm happy to finally contribute as I'm a long-time beneficiary of the site.

wjandrea Over a year ago

I could have sworn I read that lists behave as well as tuples in one-off unpackings like this, but I can't find it anymore. But yeah it makes sense that tuples perform better. Also I just noticed the parens around the names, (a, b, c, d) -- those aren't necessary.

Joseph O'Donnell Over a year ago

You're right about the unnecessary parenthesis. I updated the answer.

Collectives™ on Stack Overflow

Python Syntax for Assigning Multiple Variables Across Multiple Lines

3 Answers 3

1 Comment

Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related