Plotly Express: Scatter, Bar, Line & Histogram

The problem, from first principles

Building a figure trace by trace is flexible and wordy. Plotly Express (px) is the short way: you give it a DataFrame and column names and it creates the traces, the axis titles, the legend and a sensible colour scheme in one call. px.scatter(df, x="height", y="weight", color="species") produces one trace per species, named, coloured and listed in the legend, because a column mapped to color means "split by this".

Because Express builds ordinary plotly figures, everything it produced can be checked: how many traces, what each is called, what numbers each holds. The decisions that matter are the same as in any chart: which order the groups come in, whether to aggregate before drawing, and whether lines are sorted along the x axis. This question builds four Express charts and pins down each of those.

From theory to code

Implement scatter_by_group(df, x, y, group, order), total_bars(df, cat, value), histogram_figure(df, column, bins) and lines_by_group(df, x, y, group). The signatures and docstrings are already in the editor.

Constraints

• Use plotly.express (import plotly.express as px). Do not call fig.show().
• scatter_by_group(df, x, y, group, order) returns a scatter with one trace per value of group, the traces in the order given by order (a list of the group values), each trace holding that group's points (rows in their original order).
• total_bars(df, cat, value) returns a bar chart with one bar per category: the sum of value per category, largest total first, ties by category name ascending. Aggregate with pandas first, then draw.
• histogram_figure(df, column, bins) returns a histogram of column requesting bins bins (nbinsx).
• lines_by_group(df, x, y, group) returns a line chart with one line per group, groups in order of their first appearance in df, each line's points sorted by x ascending.

Hints