Code Sample, a copy-pastable example if possible
# Your code here
df = pd.DataFrame({'a': range(4), 'b': range(4,8)})
df.loc[df.a==2, ['a', 'b']] = df.loc[df.a==2, ['b', 'a']]
print df
produces:
a b
0 0 4
1 1 5
2 2 6
3 3 7
Problem description
This should interchange the value for column and b for when a == 2. Right now it silently does nothing.
Expected Output
a b
0 0 4
1 1 5
2 6 2
3 3 7
Output of pd.show_versions()
# Paste the output here pd.show_versions() here
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.11.final.0
python-bits: 64
OS: Darwin
OS-release: 16.5.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None
pandas: 0.19.2
nose: 1.3.6
pip: 8.1.2
setuptools: 35.0.1
Cython: 0.24
numpy: 1.12.1
scipy: 0.18.1
statsmodels: 0.8.0rc1
xarray: None
IPython: 5.2.2
sphinx: None
patsy: 0.4.1
dateutil: 2.6.0
pytz: 2016.10
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: 1.5.3
openpyxl: None
xlrd: 1.0.0
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.4.0
html5lib: 0.9999999
httplib2: 0.9.2
apiclient: None
sqlalchemy: 1.0.11
pymysql: None
psycopg2: 2.6.1 (dt dec pq3 ext lo64)
jinja2: 2.9.5
boto: 2.39.0
pandas_datareader: None
Comment From: jreback
this is shown as an example in the docs http://pandas.pydata.org/pandas-docs/stable/indexing.html#basics and is as expected
the axes align by definition
Comment From: rchurt
For anyone coming across this later, the correct way to do this is:
df = pd.DataFrame({'a': range(4), 'b': range(4,8)})
df.loc[df.a==2, ['a', 'b']] = df.loc[df.a==2, ['b', 'a']].to_numpy()
print df