python "best practice" for lists/dictionary etc

Question

Been looking over the python docs for code formatting best practice for large lists and dictionaries, eg

something = {'foo' : 'bar', 'foo2' : 'bar2', 'foo3' : 'bar3'..... 200 chars wide etc..}

or

something = {'foo' : 'bar',
             'foo2' : 'bar2',
             'foo3' : 'bar3',
             ...
             }

or

something = {
             'foo' : 'bar',
             'foo2' : 'bar2',
             'foo3' : 'bar3',
             ...
             }

and then how to handle deep nesting of lists/dictionaries...

Answer 1

I prefer the second or third one.

Reason:

1. Each element is on it's own line
2. reaching to end of line to add a new element is a pain in text editor
3. Adding a new element is easy
4. With the third option, Sometimes you can check no of elements by selecting those lines. Most editor will tell you the number of selected lines.

Answer 2

Well, the first one is a no-go, since your lines should only 79 characters wide. With regards to the other two options, I suppose it's a matter of taste, but I personally prefer the second option.

Answer 3

Define your dictionary in any way you want and then try this:

from pprint import pprint

pprint(yourDict)

# for a short dictionary it returns:

{'foo': 'bar', 'foo2': 'bar2', 'foo3': 'bar3'}

# for a longer/nested:

{'a00': {'b00': 0,
         'b01': 1,
         'b02': 2,
         'b03': 3,
         'b04': 4,
         'b05': 5,
         'b06': 6,
         'b07': 7,
         'b08': 8,
         'b09': 9},
 'a01': 1,
 'a02': 2,
 'a03': 3,
 'a04': 4,
 'a05': 5,
 'a06': 6,
 'a07': 7,
 'a08': 8,
 'a09': 9,
 'a10': 10}

Do you like the output?

Answer 4

My preferred way is:

something = {'foo': 'bar',
             'foo2': 'bar2',
             'foo3': 'bar3',
             ...
             'fooN': 'barN'}

Answer 5

Definitly NOT option 1, one of the strenghts of python is its legibility. Option 1 serverly diminishes that legibility.

Out of 2 & 3, I'll echo the same reasons pyfunc stated for both.

However in my own code I prefer option 3 simply because the first element sometimes gets 'lost' by being at the end of the declare line, and upon quick glancing at code sometimes I just won't see it immediately. I know it's a little silly but the mind works in mysterious ways ...

Answer 6

If you go by ganeti (which respects PEP 8) you should choose the third option.

something = {
             'foo1': 'bar1',
             'foo2': 'bar2',
             'foo3': 'bar3',
             ...
             }

I like this esp. because you can select only the elements you want. And I feel removing or adding elements to either ends is faster this way.

Note: As pointed out in the comment there should be no whitespace before ':' (E203) as per PEP.

Answer 7

aaronasterling's indentation style is what I prefer. This, and several other styles are explained in another SO Question. Especially Lennart Regebro's answer gave a nice overview.

But this style was the one most voted for:

my_dictionary = {
    1: 'something',
    2: 'some other thing',
}

Answer 8

I love the second way:

something = {'foo' : 'bar',
         'foo2' : 'bar2',
         'foo3' : 'bar3',
         ...
         'fooN': 'barN'}

Answer 9

Previous to reading this post I would have opted for the third option you give. But now I might go for the one that is NOT Török Gábor's style:

my_dictionary = { 1: 'something', 2: 'some other thing', }

But honestly anything aside from your first option is probably fine.