`to_plotly_json` does not handle `np.array` properly

[ChiQiao]

Code to reproduce the issue:

import json
import plotly.graph_objects as go
import numpy as np

fig = go.Figure(go.Scatter(x=np.array([0, 1]), y=np.array([0, 1])))
json.dumps(fig.to_plotly_json())  # TypeError: Object of type ndarray is not JSON serializable

[itsluketwist]

@ChiQiao - Hey! Whilst the to_plotly_json method doesn't provide a dict that is immediately json compatible, if you use the PlotlyJSONEncoder as the cls arg when creating the json then everything should work fine. 😄

Fixed code snippet:

import json
import plotly.graph_objects as go
import numpy as np

from plotly.utils import PlotlyJSONEncoder  # need this import

fig = go.Figure(go.Scatter(x=np.array([0, 1]), y=np.array([0, 1])))
json.dumps(fig.to_plotly_json(), cls=PlotlyJSONEncoder)  # encoder used as arg here, handles the numpy data  (amongst others)

Hopefully this fixes your issue!

[ChiQiao]

@itsluketwist Thanks for the information. Do you think this is the expected behavior (i.e., fulfilling the purpose of this method as Convert figure to a JSON representation as a Python dict)? If so, please feel free to close this issue.

[itsluketwist]

@ChiQiao - agreed, this experience could be better. I've made a PR to hopefully make it so, and discuss the json usage with project maintainers. 😄

[ChiQiao]

@ChiQiao - agreed, this experience could be better. I've made a PR to hopefully make it so, and discuss the json usage with project maintainers. 😄

Awesome. As a side note, do you know the difference between the to_json and to_plotly_json methods, besides the fact that one returns str and the other returns dict? Based on the simple test below, the underlying dictionary is the same.

fig = go.Figure(go.Scatter(x=np.array([0, 0]), y=np.array([0, 1]), marker={"color": [0, np.nan]}))
json.loads(json.dumps(fig.to_plotly_json(), cls=PlotlyJSONEncoder)) == json.loads(fig.to_json())  # True

[itsluketwist]

@ChiQiao - I don't know the reason for the multiple very similar functions here, especially when there is also a to_dict method that is the same as to_plotly_json. 😅

You're right that the to_json method should also fix your problem! 😄

[alexcjohnson]

Closed by #4301 - thanks @itsluketwist 🎉