Add index=False option to_markdown()

Problem description

This is a feature request to add an optional index=False argument to the new to_markdown() dataframe method. This would produce a markdown table without the initial unnamed index column.

[dsaxton]

This is actually possible by passing showindex=False, but could probably be better documented (it’s one of the tabulate kwargs):

In [1]: import pandas as pd       
                                                                                                                                                                                                        
In [2]: df = pd.DataFrame({"a": [1, 2, 3]})              
                                                                                                                                                                                 
In [3]: print(df.to_markdown(showindex=False))                                                                                                                                                                                            
|   a |
|----:|
|   1 |
|   2 |
|   3 |

[chrisjcameron]

What should the behaviour be if user set both showindex and index? Which one should take the priority or should I raise an ValueError

I think most users will be expecting pandas-like keywords to work, so I would prioritize those. An alternative might be a warning about “When both index and showindex are set, one value will be used but which is undefined”. This would at least give users a clue that these need not both be specified but gives a lot of latitude for future refinement that changes the behavior.