Why does Pycharm's inspector complain about "d = {}"?

Question

When initializing a dictionary with d = {} Pycharm’s code inspector generates a warning, saying

This dictionary creation could be rewritten as a dictionary literal.

If I rewrite it d = dict() the warning goes away. Since {} already is a dictionary literal, I’m pretty sure the message is erroneous. Furthermore, it seems like both d = {} and d = dict() are valid and Pythonic.

This related question seems to conclude that the choice is just a matter of style/preference:
differences between "d = dict()" and "d = {}"

Why would Pycharm complain about d = {}?

UPDATE:

Mac nailed it. The warning actually applied to multiple lines, not just the one that was flagged.

Pycharm seems to look for a sequence of consecutive statements where you initialize a dictionary and then set values in the dictionary. For example, this will trigger the warning:

d = {}
d['a'] = 1

But this code will not:

d = {}
pass
d['a'] = 1

Asked By: Chris Sears

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Source

Answer 1

What is the code following your dictionary declaration?

I think PyCharm will trigger the error if you have something like:

dic = {}
dic['aaa'] = 5

as you could have written

dic = {'aaa': 5}

Note: The fact that the error goes away if you use the function dict(). This doesn’t necessarily mean that pycharm believes dict() is a literal. It could just mean that it doesn’t complain about it:

dic = dict()
dic['aaa'] = 5

Answered By: mac

Answer 2

for those who like (just like me) to initialize dictionaries with single operation

d = {
  'a': 12,
  'b': 'foo',
  'c': 'bar'
}

instead of many lines like

d = dict()
d['a'] = 12
d['b'] = ....

in the end I ended up with this:

d = dict()
d.update({
  'a': 12,
  'b': 'foo',
  'c': 'bar'
})

Pycharm is not complaining on this

Answered By: Igor.K

Answer 3

This can be disabled in the Project Settings or Default Settings.

Navigate to Settings -> Inspections -> Python
Uncheck “Dictionary creation could be rewritten by dictionary literal”

Answered By: Craig Jackson

Answer 4

mydict = {
  a: 5,
  b:z+c/2
}

The dictionary could have been created directly without initialising them first and then reassigning new values.

Answered By: Asnim P Ansari

Answer 5

I have a situation where this warning is bugging the hell out of me. In my case, I’m populating my dict partially as literals and partially from a tuple output by a function, like so:

def get_other_values():
    return 3, 4

foo = {
    "a": 1,
    "b": 2
}
foo["c"], foo["d"] = get_other_values()

So, unless I create interim vars for the output of get_other_values, PEP8 generates this warning even though I’m creating the dict with literals. And I can’t assign the c and d keys in the literal, since the values are output as a tuple.

Answered By: Chris Woodfield

Why does Pycharm's inspector complain about "d = {}"?

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