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pd.Timedelta is not JSON serializable

See original GitHub issue

In:

td =  pd.timedelta_range(0,periods=3,freq='h')
alt.Chart(
    pd.DataFrame(dict(id=np.arange(td.size),timedelta = td))
).mark_bar(
).encode(
 x = 'timedelta',
 y ='id:O'
)

Out:

~/anaconda/anaconda/envs/rr_dev/lib/python3.5/json/encoder.py in default(self, o)
    177 
    178         """
--> 179         raise TypeError(repr(o) + " is not JSON serializable")
    180 
    181     def encode(self, o):

TypeError: Timedelta('0 days 00:00:00') is not JSON serializable

In:

print ('pandas',pd.__version__)
print ('altair',alt.__version__)

Out:

pandas 0.23.0
altair 2.1.0

Expected, but I’m not sure that is achievable without timeUnit="hoursminutes". visualization 17

Issue Analytics

State:
Created 5 years ago
Comments:11 (11 by maintainers)

Top GitHub Comments

1reaction

jakevdpcommented, Jun 26, 2018

OK, I’ve added a better error in #974

0reactions

jonathangjertsencommented, Jan 11, 2021

For future reference, I ended up with a workaround like this:

def add_difference_column(data, column, difference_column):
    diffed = data[column].diff()

    # Special case for timestamps due to https://github.com/altair-viz/altair/issues/967
    if diffed.dtype.kind == "m":
        diffed = diffed.dt.total_seconds()

    data[difference_column] = diffed

add_difference_column(data, "temperature", "temperature_diff")
add_difference_column(data, "voltage", "voltage_diff")
add_difference_column(data, "time", "time_diff")
# etc

If Altair/Vega supported timedeltas out of the box, this could be reduced to

def add_difference_column(data, column, difference_column):
    data[difference_column] = data[column].diff()

(the helper function is not strictly needed in this reduced example, but in my actual usecase this is part of a more complex operation with some filtering and grouping before and after)

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