How to check if a column exists in Pandas

Question

Is there a way to check if a column exists in a Pandas DataFrame?

Suppose that I have the following DataFrame:

>>> import pandas as pd >>> from random import randint >>> df = pd.DataFrame({'A': [randint(1, 9) for x in xrange(10)],                        'B': [randint(1, 9)*10 for x in xrange(10)],                        'C': [randint(1, 9)*100 for x in xrange(10)]}) >>> df    A   B    C 0  3  40  100 1  6  30  200 2  7  70  800 3  3  50  200 4  7  50  400 5  4  10  400 6  3  70  500 7  8  30  200 8  3  40  800 9  6  60  200 

and I want to calculate df['sum'] = df['A'] + df['C']

But first I want to check if df['A'] exists, and if not, I want to calculate df['sum'] = df['B'] + df['C'] instead.

Answer 1

This will work:

if 'A' in df: 

But for clarity, I'd probably write it as:

if 'A' in df.columns: 

Answer 2

To check if one or more columns all exist, you can use set.issubset, as in:

if set(['A','C']).issubset(df.columns):    df['sum'] = df['A'] + df['C']                 

As @brianpck points out in a comment, set([]) can alternatively be constructed with curly braces,

if {'A', 'C'}.issubset(df.columns): 

See this question for a discussion of the curly-braces syntax.

Or, you can use a generator comprehension, as in:

if all(item in df.columns for item in ['A','C']):