[PROPOSAL] Make Series.update() accept a dictionary

Code Sample, a copy-pastable example if possible

I propose to re-write the Series.update() method to accept a dictionary object. This would be useful for example when you are iterating over a DataFrame using DataFrame.iterrows(), and you want to update the row object returned by iterrows() in order to build another DataFrame starting from the DataFrame you are iterating over

Here is an example that doesn’t work:

import pandas as pd
s = pd.Series({'city':'Rome'})
s.update({'country':'Italy'})

Problem description

Traceback (most recent call last): File “<stdin>”, line 1, in <module> File “C:\InstalledPrograms\Anaconda3\lib\site-packages\pandas\core\series.py”, line 2807, in update other = other.reindex_like(self) AttributeError: ‘dict’ object has no attribute ‘reindex_like’

Simple use case

In this use case, an explicit conversion to dict() is needed

import random
import pandas as pd

def very_long_dictionary():
    d = dict()
    for c in range(2,10):
        d[c] = random.randint(1,101)
    return d

df = pd.DataFrame([[1,2],[3,4],[5,6]])
print(df)

outdl = list()
for index,row in df.iterrows():
    #Explicit conversion to dict is needed
    row = dict(row)
    row.update(very_long_dictionary())
    outdl.append(row)
newdf = pd.DataFrame(outdl)
print(newdf)

Expected Output

The series would update to the new value

Output of pd.show_versions()

pd.show_versions()

INSTALLED VERSIONS

commit : None python : 3.7.7.final.0 python-bits : 64 OS : Windows OS-release : 10 machine : AMD64 processor : Intel64 Family 6 Model 158 Stepping 10, GenuineIntel byteorder : little LC_ALL : None LANG : None LOCALE : None.None

pandas : 1.0.3 numpy : 1.18.1 pytz : 2019.3 dateutil : 2.8.1 pip : 20.0.2 setuptools : 46.1.3.post20200330 Cython : 0.29.15 pytest : 5.4.1 hypothesis : 5.5.4 sphinx : 2.4.4 blosc : None feather : None xlsxwriter : 1.2.8 lxml.etree : 4.5.0 html5lib : 1.0.1 pymysql : None psycopg2 : None jinja2 : 2.11.1 IPython : 7.13.0 pandas_datareader: None bs4 : 4.8.2 bottleneck : 1.3.2 fastparquet : None gcsfs : None lxml.etree : 4.5.0 matplotlib : 3.1.3 numexpr : 2.7.1 odfpy : None openpyxl : 3.0.3 pandas_gbq : None pyarrow : None pytables : None pytest : 5.4.1 pyxlsb : None s3fs : None scipy : 1.4.1 sqlalchemy : 1.3.15 tables : 3.6.1 tabulate : None xarray : None xlrd : 1.2.0 xlwt : 1.3.0 xlsxwriter : 1.2.8 numba : 0.48.0

[dsaxton]

How about wrapping your dict in a Series before passing to update? (Also I’m not sure if your example s.update({‘country’:‘Italy’}) will do what you want since ‘country’ isn’t in the index of s.)

I do think though that this could probably use a better error message.

[dericke]

@dsaxton I submitted a PR to close this.