[BUG] error with size kw in px functions and non-str argument

[emmanuelle]

import numpy as np
import plotly.express as px
df = px.data.gapminder()
fig = px.scatter(df, x=df.gdpPercap, y=df.lifeExp, color=df.continent, size=df.pop,
                facet_col=df.year, facet_col_wrap=4)
fig.show()

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-b52564550e30> in <module>
      3 df = px.data.gapminder()
      4 fig = px.scatter(df, x=df.gdpPercap, y=df.lifeExp, color=df.continent, size=df.pop,
----> 5                 facet_col=df.year, facet_col_wrap=4)
      6 fig.show()

~/code/plotly.py/packages/python/plotly/plotly/express/_chart_types.py in scatter(data_frame, x, y, color, symbol, size, hover_name, hover_data, custom_data, text, facet_row, facet_col, facet_col_wrap, error_x, error_x_minus, error_y, error_y_minus, animation_frame, animation_group, category_orders, labels, color_discrete_sequence, color_discrete_map, color_continuous_scale, range_color, color_continuous_midpoint, symbol_sequence, symbol_map, opacity, size_max, marginal_x, marginal_y, trendline, trendline_color_override, log_x, log_y, range_x, range_y, render_mode, title, template, width, height)
     53     in 2D space.
     54     """
---> 55     return make_figure(args=locals(), constructor=go.Scatter)
     56 
     57 

~/code/plotly.py/packages/python/plotly/plotly/express/_core.py in make_figure(args, constructor, trace_patch, layout_patch)
   1099 
   1100     args, trace_specs, grouped_mappings, sizeref, show_colorbar = infer_config(
-> 1101         args, constructor, trace_patch
   1102     )
   1103     grouper = [x.grouper or one_group for x in grouped_mappings] or [one_group]

~/code/plotly.py/packages/python/plotly/plotly/express/_core.py in infer_config(args, constructor, trace_patch)
    975             all_attrables += [group_attr]
    976 
--> 977     args = build_dataframe(args, all_attrables, array_attrables)
    978 
    979     attrs = [k for k in attrables if k in args]

~/code/plotly.py/packages/python/plotly/plotly/express/_core.py in build_dataframe(args, attrables, array_attrables)
    939                 else:  # numpy array, list...
    940                     col_name = _check_name_not_reserved(field, reserved_names)
--> 941                 if length and len(argument) != length:
    942                     raise ValueError(
    943                         "All arguments should have the same length. "

TypeError: object of type 'method' has no len()

(the problem is with the size argument)

[nicolaskruchten]

Hehe yeah this df.col_name pattern falls over when col_name conflicts with a field or method defined on df such as df.pop() or df.size... We should probably have a special message for when len isn't defined to catch some/most of these. Possibly a separate error path for when people are passing in an unbound function like pop or something too?

[emmanuelle]

Oh of course df.pop is a method I had not understood the error message correctly. On the one hand it's not as bad as I thought (df.pop is not a valid argument) but the error message is still confusing. Yes, testing whether the argument is a function sounds like a good solution.

[gvwilson]

Hi - we are currently trying to tidy up Plotly's public repositories to help us focus our efforts on things that will help users most. Since this issue has been sitting for several years, I'm going to close it. If it's still a concern, we'd be grateful if you could open a new issue (with a short reproducible example if appropriate) so that we can add it to our backlog. Thanks for your help - @gvwilson