
The eval() method in pandas uses string expressions to efficiently compute operations on a dataframe.
Syntax –
dataframe.eval(expr, inplace, kwargs)
expr – The expression string to evaluate.
inplace – whether to perform the operation inplace and mutate the existing DataFrame. Otherwise, a new DataFrame is returned.
Examples –
Let’s create a DataFrame to work with.
import pandas as pd
df = pd.DataFrame({'A':[1, 2, 3, 4, 5],
'B': [6, 7, 8, 9, 10]})
df

Let’s say that you want to add the columns A and B together and create a new column C. One way to do that is
df['C'] = df['A'] + df['B']

You can do the same operation using the eval() method like this –
df.eval('C = A + B', inplace=True)

Multiple columns can be assigned to using multi-line expressions.
df.eval(
"""
C = A + B
D = A - B
"""
)
