Replace with bfill, ffill or pad on DataFrame · Issue #19632 · pandas-dev/pandas (original) (raw)

Code Sample, a copy-pastable example if possible

With a Series replace with method equal to 'bfill', 'ffill' or 'pad' and value=None works as expected

In [1]: s = pd.Series([0, 1, 2, 3, 4]) In [2]: s.replace([1, 2], method='bfill') Out[2]: 0 0 1 3 2 3 3 3 4 4 dtype: int64 In [3]: s.replace(1, method='bfill') Out[3]: 0 0 1 2 2 2 3 3 4 4 dtype: int64

But for a DataFrame with a list or scalar it throws an error:

In [4]: df = pd.DataFrame({'A': [0, 1, 2, 3, 4], 'B': [0, 1, 2, 3, 4], 'C': ['a', 'b', 'c', 'd', 'e']})

In [5]: df.replace(to_replace=[1, 2], value=None, method='bfill') Out[5]:

TypeError Traceback (most recent call last) in () ----> 1 df.replace(2, method='bfill')

~/anaconda3/lib/python3.6/site-packages/pandas/core/generic.py in replace(self, to_replace, value, inplace, limit, regex, method, axis) 4492 if isinstance(to_replace, (tuple, list)): 4493 return _single_replace(self, to_replace, method, inplace, -> 4494 limit) 4495 4496 if not is_dict_like(to_replace):

~/anaconda3/lib/python3.6/site-packages/pandas/core/generic.py in _single_replace(self, to_replace, method, inplace, limit) 74 if self.ndim != 1: 75 raise TypeError('cannot replace {0} with method {1} on a {2}' ---> 76 .format(to_replace, method, type(self).name)) 77 78 orig_dtype = self.dtype TypeError: cannot replace [[1, 2]] with method bfill on a DataFrame

In [6]: df.replace(to_replace=2, value=None, method='bfill') Out[6]: TypeError Traceback (most recent call last) in () ----> 1 df.replace(2, method='bfill')

~/anaconda3/lib/python3.6/site-packages/pandas/core/generic.py in replace(self, to_replace, value, inplace, limit, regex, method, axis) 4492 if isinstance(to_replace, (tuple, list)): 4493 return _single_replace(self, to_replace, method, inplace, -> 4494 limit) 4495 4496 if not is_dict_like(to_replace):

~/anaconda3/lib/python3.6/site-packages/pandas/core/generic.py in _single_replace(self, to_replace, method, inplace, limit) 74 if self.ndim != 1: 75 raise TypeError('cannot replace {0} with method {1} on a {2}' ---> 76 .format(to_replace, method, type(self).name)) 77 78 orig_dtype = self.dtype

TypeError: cannot replace [2] with method bfill on a DataFrame

Should the DataFrame case work in the same way as the Series or is this simply a user-error on my part?

Expected Output

DataFrame.replace(method=) to work in a similar way to Series.replace(method=)

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.6.3.final.0
python-bits: 64
OS: Linux
OS-release: 4.13.0-32-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_IE.UTF-8
LOCALE: en_IE.UTF-8

pandas: 0.22.0
pytest: 3.2.1
pip: 9.0.1
setuptools: 36.5.0.post20170921
Cython: 0.26.1
numpy: 1.14.0
scipy: 0.19.1
pyarrow: None
xarray: None
IPython: 6.1.0
sphinx: 1.6.3
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2018.3
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.2
feather: None
matplotlib: 2.1.0
openpyxl: 2.4.8
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.2
lxml: 4.1.0
bs4: 4.6.0
html5lib: 0.999999999
sqlalchemy: 1.1.13
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None