[Pandas-dev] Help with contributing

[Robert Butler]

Hi Pandas dev

I am developing a small web application using flask and pandas
Part of it involved making an api call using fetch to the server, and the server had to return some data formatted as html

The code that executes during the fetch request does a lot, and when I used the dataframe.to_html() method it took a while

I spent some time making a function that converts a dataframe to html and I was able to get something that runs a lot faster, and the difference is pretty noticeable when the dataframe is a lot larger

When I looked at the source code, it seemed like it would be difficult to incorporate the function as a contribution, so I was wondering if I could get some help?

I have roughly 2 years of experience with programming in python, and did not major in CS, so I consider myself to be a beginner, which Is why I struggle with something basic like making a contribution like this

I was wondering if I could get some help making this contribution?

This is the function, obviously you can tell I sort of wrote it in such a way that it would be convenient for my particular application

def htmltable(df, id = None, cssclass = None, enumeraterows = True):
    '''
        df is a pandas dataframe,
        id is a css id you want to give to the table,
        cssclass is a css class for the table,
        enumeraterows actually only distinguishes even/odd rows with css classes
    '''

    html = """
    <table{}{}>
        <colgroup>
            {}
        </colgroup>
        <thead>
            {}
        </thead>
        <tbody>
            {}
        </tbody>
    </table>
    """.format(
        # add in the id
        f" id = {id}" if id else "",

        # add the class
        f" class = {cssclass}" if cssclass else "",

        # colgroups
        ''.join(['<col span="1" class="{}">'.format(colname) for colname in df.columns]),

        # column headers
        ''.join(
            [
                # sticks on the outsides of the row after doing the join
                '<tr><th scope="col">{}</th></tr>'.format(
                    '</th><th scope="col">'.join(df.columns)
                )
            ]
        ),
        # cells of table body
        ''.join(
            [
                # sticks on the outsides of the row after doing the join
                # adds even and odd css classes to each row as well
                '<tr{} id="rownumber-{}">{}</tr>'.format(
                    ' class="row-even"' if i % 2 == 0 else ' class="row-odd"' if enumeraterows else "",
                    i,
                    x
                ) for i,x in
                # Zips columns together, then joins them with closing table cell tag and opening table cell tag between
                enumerate([''.join(
                    list(
                        map(
                            lambda cell:
                            '<td contenteditable="true" class="colname-{}">{}</td>'.format(cell['column_name'], cell['column_value']),
                            row
                        )
                    )
                )
                for row in
                    zip(*
                        [
                            df[col].apply(lambda x: {'column_name':col, 'column_value': x}) for col in df.columns
                        ]
                    )
                ])
            ]
        )
    )
    return html



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