Misleading error message when an invalid y column name is provided to px.line
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bug
P3
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- Python
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Description
When attempting to plot multiple y values using px.line (or similar), erroneous column names lead to a misleading error message that states that the length of the arguments is incorrect, when in fact the problem is that there the column name is wrong.
Simple to reproduce:
import plotly.express as px
import pandas as pd
import numpy as np
x = np.linspace(0, 10, 100)
data1 = x**2
data2 = x**3
df = pd.DataFrame({"x": x, "data1": data1, "data2": data2})
px.line(df, x = "x", y = ["data1", "data2"]) # works fine
px.line(df, x = "x", y = ["data1", "Data2"])
# this last line gives a misleading error message:
# ValueError: All arguments should have the same length. The length of argument `y` is 2,
# whereas the length of previously-processed arguments ['x'] is 100
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First steps
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Research direction
Start by running the issue's pandas and NumPy reproduction with px.line, then trace the validation path used for the x and y arguments. Done means an invalid y column name produces an accurate column-related error while valid multiple-y input continues to work; the payload does not name a specific file or test.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- data-visualization
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100