EHN encoding parameter for to_latex

[nbonnotte]

closes #7061

I'm working on solving issue #7061: currently, with Python 2 it is not possible to use .to_latex() when the dataframe contains utf-8 strings. This PR adds an encoding parameter to make it possible.

The work is not completely done though, and I'm making this PR to start a discussion here. In its current state, the PR quickly fixes the issue and provides tests, so it is kind of a minimal PR.

@jreback in the discussion on issue #7061, you made the following suggestion:

you may want to add a LatexFormatter (as a sub-class of DataFrameFormatter) as this will allow some re-factoring to be internally done later on.

I would be glad to work in that direction, but I'm a bit confused by the current organization of the code. This LatexFormatter would seem to me to be similar to HTMLFormatter, which inherits from TableFormatter (exactly as DataFrameFormatter). In that case, DataFrameFormatter would use LatexFormatter for .to_latex() exactly as it uses HTMLFormatter for .to_html(). Is that what you had in mind?

[jreback]

put the import at the top of the module

[jreback]

@nbonnotte what I mean is that I think a LatexFormatter be created in format.py which is like HTMLFormatter (its a sub-class of TableFormatter). So you don't have all of the latex formatting code living in to_latex itself (which instead just instantiates a class and calls .write_result, similarly to to_html).

This will allow easier refactoring later.

[nbonnotte]

BTW, this does not solves the missing decimal parameter I mentioned in the discussion of issue #7061

[jreback]

@nbonnotte what was the decimal issue? (can't seem to find it in that issue)

[nbonnotte]

I just meant the decimal parameter is still lacking, I didn't add it. I should do another PR to do that.

[jreback]

add the issue number (7061)

[jreback]

@nbonnotte create another issue for the decimal parameter (we are going to close #7061) with this PR

[jreback]

comments, ping when green.

[nbonnotte]

I've created another issue for decimal (#12031)

Working on the docstring, I realized there was something odd: I was initializing LatexFormatter with a DataFrameFormatter and a variable strcols containing the result of DataFrameFormatter._to_str_columns.

I think it is simpler if the parameter strcols is removed and the call to DataFrameFormatter._to_str_columns is performed in LatexFormatter. You can see in the 2nd commit the changes (dc425cb0e959ccab2941cab27f329ec41cb768d7).

There is still one thing that bothers me: now I'm calling a "private" method (_to_str_columns) from outside (that is, from LatexFormatter). Is that a problem?

[jreback]

@nbonnotte no that's ok

[nbonnotte]

I've squashed my commits then.

All green!

[jreback]

are you using these variables? (e.g. .columns); I'd rather you not define them, or use a cached-property if its more clear (e.g. for .frame)

[jreback]

pls git diff master | flake8 --diff

[nbonnotte]

@jreback should be good now ^^

[jreback]

merged via 3a832df

thanks!