MPLD3 with Python error

Question

I tried to replicate the example found on this website: http://mpld3.github.io/examples/scatter_tooltip.html

But I get the following error: Object of type 'ndarray' is not JSON serializable

I can't figure out what I need to change.

Here's the code:

import matplotlib.pyplot as plt
import numpy as np
import mpld3

fig, ax = plt.subplots(subplot_kw=dict(axisbg='#EEEEEE'))
N = 100

scatter = ax.scatter(np.random.normal(size=N),
                     np.random.normal(size=N),
                     c=np.random.random(size=N),
                     s=1000 * np.random.random(size=N),
                     alpha=0.3,
                     cmap=plt.cm.jet)
ax.grid(color='white', linestyle='solid')

ax.set_title("Scatter Plot (with tooltips!)", size=20)

labels = ['point {0}'.format(i + 1) for i in range(N)]
tooltip = mpld3.plugins.PointLabelTooltip(scatter, labels=labels)
mpld3.plugins.connect(fig, tooltip)

mpld3.show()

The exact error is:

Traceback (most recent call last):
  File "C:\Program Files\JetBrains\PyCharm 2017.3.1\helpers\pydev\pydev_run_in_console.py", line 52, in run_file
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "C:\Program Files\JetBrains\PyCharm 2017.3.1\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "C:/Users/Main/PycharmProjects/Macrobond_API/scenario testing.py", line 22, in <module>
    mpld3.show()
  File "C:\Users\Main\AppData\Local\Programs\Python\Python36-32\lib\site-packages\mpld3\_display.py", line 358, in show
    html = fig_to_html(fig, **kwargs)
  File "C:\Users\Main\AppData\Local\Programs\Python\Python36-32\lib\site-packages\mpld3\_display.py", line 251, in fig_to_html
    figure_json=json.dumps(figure_json, cls=NumpyEncoder),
  File "C:\Users\Main\AppData\Local\Programs\Python\Python36-32\lib\json\__init__.py", line 238, in dumps
    **kw).encode(obj)
  File "C:\Users\Main\AppData\Local\Programs\Python\Python36-32\lib\json\encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "C:\Users\Main\AppData\Local\Programs\Python\Python36-32\lib\json\encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "C:\Users\Main\AppData\Local\Programs\Python\Python36-32\lib\site-packages\mpld3\_display.py", line 138, in default
    return json.JSONEncoder.default(self, obj)
  File "C:\Users\Main\AppData\Local\Programs\Python\Python36-32\lib\json\encoder.py", line 180, in default
    o.__class__.__name__)
TypeError: Object of type 'ndarray' is not JSON serializable

Answer 1

There is an open issue raised against this error, the link is https://github.com/mpld3/mpld3/pull/435

One work-around is to edit the mpld3/_display.py file inside your mpld3 module, the edit will be on below default function

before:

def default(self, obj):
    if isinstance(obj, (numpy.int_, numpy.intc, numpy.intp, numpy.int8,
        numpy.int16, numpy.int32, numpy.int64, numpy.uint8,
        numpy.uint16,numpy.uint32, numpy.uint64)):
        return int(obj)
    elif isinstance(obj, (numpy.float_, numpy.float16, numpy.float32, 
        numpy.float64)):
        return float(obj)
    return json.JSONEncoder.default(self, obj)

after:

def default(self, obj):
    if isinstance(obj, (numpy.int_, numpy.intc, numpy.intp, numpy.int8,
        numpy.int16, numpy.int32, numpy.int64, numpy.uint8,
        numpy.uint16,numpy.uint32, numpy.uint64)):
        return int(obj)
    elif isinstance(obj, (numpy.float_, numpy.float16, numpy.float32, 
        numpy.float64)):
        return float(obj)
    elif isinstance(obj, (numpy.ndarray,)): # add this line
        return obj.tolist() # add this line
    return json.JSONEncoder.default(self, obj)

basically you just added

elif isinstance(obj, (numpy.ndarray,)): # add this line
            return obj.tolist() # add this line