CODEWITHSUNDEEP
pythonpandas
Spring
Spring

Reputation: 193

Select columns by matching column name

I have a pd df and I want to select one of the columns by matching the column names.

For example, if I have a defined value called "division =2". I want to use that to select related column from the following table. In this case, I want to get column df.iloc[:, 2].

How do I do this?

 division=2 

        Year       1        2          3       4
  0     2024      1.007351 1.098082 1.033620   0.938746
  1     2025      1.023808 1.117399 1.036366   0.936205
  2     2026      1.036785 1.133247 1.040184   0.934735

Upvotes: 0

Views: 364

Answers (1)

s3dev
s3dev

Reputation: 9701

You are very nearly there! See below. You can use your division variable in place of the column name (or locator, in this case).

A word of caution: It's important to note, the difference in column name and locator. The OP asks for column name but is using the locator (df.iloc) in the question.

Locator:
.iloc[:, 2] will return all rows in the third column (numbering starts at 0). And this can vary as this DataFrame was created via a dict, which does not retain order.

Column Name:
df[2] or df.loc[:, 2] will return all rows in the column named 2.

import pandas as pd

division = 2
data = {'Year': [2024, 2025, 2026],
        1: [1.007351, 1.023808, 1.036785],
        2: [1.098082, 1.117399, 1.133247],
        3: [1.033620, 1.036366, 1.040184],
        4: [0.938746, 0.936206, 0.934735]}

df = pd.DataFrame(data)

# Display DataFrame
print(df)
# 1) Display the output of column named 2.
print(df[division])
# 2) Display the output of column 2.
print(df.iloc[:, division])

DataFrame contents:

          1         2         3         4  Year
0  1.007351  1.098082  1.033620  0.938746  2024
1  1.023808  1.117399  1.036366  0.936206  2025
2  1.036785  1.133247  1.040184  0.934735  2026

1) Output for column name:

print(df[division])
0    1.098082
1    1.117399
2    1.133247
Name: 2, dtype: float64

2) Output for column locator:

print(df.iloc[:, division])
0    1.033620
1    1.036366
2    1.040184
Name: 3, dtype: float64

Upvotes: 2

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