AttributeError: 'DataFrame' object has no attribute 'series' in pandas

Question

I am trying to check if rows in a certain column of my dataframe contain the minus sign " - ".

Here is my code. I get data from a csv file and split a column up into a few columns.

import pandas as pd
df = pd.read_csv("C:/data.csv")
split_df = df["Maths Formula"].str.split("+", expand=True,)

if (split_df[[2]].str.contains(" - ")).any():
    print("contains minus")

First 3 lines run fine, but when I run

if (split_df[[2]].str.contains(" - ")).any():
    print("contains minus")

I get the error AttributeError: 'DataFrame' object has no attribute 'series'

However if I use a string to specify the column name of "df", it can run fine (below)

if (df["Maths Formula"].str.contains(" - ")).any() :

I'm not sure what is happening here. Is using string to specify a column different from using column index? Or perhaps df and split_df are 2 different types of dataframe? Or is there something else at work here?

Any help is very much appreciated!

Do you mean split_df[2] (which'll give a single column as a Series) instead of split_df[[2]] (which gives you single column DataFrame) ? — Jon Clements
– Jon Clements, Commented Jun 10, 2022 at 11:01

Daniel Tchoń · Accepted Answer · 2022-06-10 11:06:52Z

2

The method .str is defined for data Series (eg. columns), but not DataFrames (tables). It requires an attribute series to be defined. In your case, in line 5 you slice the DataFrame with the 2nd column:

split_df[[2]]

This syntax returns a DataFrame with one column. Instead, you should be indexing and accessing the 2nd series:

split_df[2]

This returns a Series-type object, which has a series attribute and thus can be converted to string. This is also why df["Maths Formula"] works - it returns a Series object.

answered Jun 10, 2022 at 11:06

Daniel Tchoń

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