Implement DataFrame.info

[HyukjinKwon]

This PR proposes DataFrame.info.

>>> import databricks.koalas as ks
>>> ks.range(100).info()
<class 'databricks.koalas.frame.DataFrame'>
Index: 100 entries, 0 to 99
Data columns (total 1 columns):
id    100 non-null int64

Resolves #872

[ueshin]

Yeah, we should in a separate PR.

[ueshin]

LGTM, pending tests.

[codecov-io]

Codecov Report

Merging #1124 into master will decrease coverage by <.01%.
The diff coverage is 93.33%.

@@            Coverage Diff            @@
##           master   #1124      +/-   ##
=========================================
- Coverage   95.11%   95.1%   -0.01%     
=========================================
  Files          35      35              
  Lines        7019    7033      +14     
=========================================
+ Hits         6676    6689      +13     
- Misses        343     344       +1

Impacted Files	Coverage Δ
databricks/koalas/missing/frame.py	100% <ø> (ø)	⬆️
databricks/koalas/frame.py	96.82% <100%> (+0.01%)	⬆️
databricks/koalas/indexes.py	96.24% <88.88%> (-0.26%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0af6c1c...89f5b2d. Read the comment docs.

[softagram-bot]

Softagram Impact Report for pull/1124 (head commit: 89f5b2d)

⚠️ Copy paste found

ℹ️ frame.py: Copy paste fragment on line 5771 shared with ../namespace.py:

              on: Union[str, List[str], Tuple[str, ...], List[Tuple[str, ...]]] = None,
              left_on: Union[str, List[str], Tuple[s...(truncated 273 chars)

ℹ️ frame.py: Copy paste fragment inside the same file on lines 7269, 7352:

        # TODO: there is a similar logic to transpose in, for instance,
        #  DataFrame.any, Series.quantile. Maybe ...(truncated 1065 chars)

ℹ️ frame.py: Copy paste fragment inside the same file on lines 4900, 4921:

            sdf = self._sdf.select(
                self._internal.index_scols +
                [self._internal.scol_for(idx...(truncated 466 chars)

ℹ️ indexes.py: Copy paste fragment inside the same file on lines 720, 1091:

            raise NotImplementedError(
                \"Doesn't support symmetric_difference between Index & MultiIndex for now\")

        sdf_self = self._kdf._s...(truncated 477 chars)

Now that you are on the file, it would be easier to pay back some tech. debt.

⭐ Change Overview

(Open in Softagram Desktop for full details)

📄 Full report

• Permalink: Full report for pull/1124

Impact Report explained. Give feedback on this report to [email protected]