Empty dataframe creation

[0x0L]

Hello,

Creating an empty dataframe with specified columns

pd.__version__
# '0.24.2'

%timeit pd.DataFrame([], columns=['a'])
# 1.57 ms ± 20.9 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

is way slower than it should be:

%timeit pd.DataFrame([])
# 184 µs ± 1.68 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

%timeit pd.DataFrame([[1]], columns=['a'])
# 343 µs ± 3.33 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

[jreback]

this is premature optimization

why does this matter in the real world?

[0x0L]

I'm reading from batch records from an API and batches can be empty.
It's just a surprising behavior. Once you noticed, it's nothing that can't be fixed one way or another...

[jreback]

if u think can be fixed w/on adding complexity then pls submit a PR

[simonjayhawkins]

can also use examples from OP of #28188 as additional benchmarks.