Use the brackets to select a single pandas DataFrame column and not dot notation

pandas Sep 13, 2019

pandas offers its users two choices to select a single column of data and that is with either brackets or dot notation. In this article, I suggest using the brackets and not dot notation for the following ten reasons.

  1. Select column names with spaces
  2. Select column names that have the same name as methods
  3. Select columns with variables
  4. Select non-string columns
  5. Set new columns
  6. Select multiple columns
  7. Dot notation is a strict subset of the brackets
  8. Use one way which works for all situations
  9. Auto-completion works in the brackets and following it
  10. Brackets are the canonical way to select subsets for all objects

Selecting a single column

Let’s begin by creating a small DataFrame with a few columns

import pandas as pd
df = pd.DataFrame({'name': ['Niko', 'Penelope', 'Aria'],
'average score': [10, 5, 3],
'max': [99, 100, 3]})

Let’s select the name column with dot notation. Many pandas users like dot notation.

0 Niko
1 Penelope
2 Aria


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Pandas Cookbook — Develop Powerful Routines for Exploring Real-World Datasets

pandas Jul 18, 2019

In this article, I will discuss the overall approach I took to writing Pandas Cookbook along with highlights of each chapter.

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Pandas Cookbook Guiding Principles

I had three main guiding principles when writing the book:

  • Use of real-world datasets
  • Focus on doing data analysis
  • Writing modern, idiomatic pandas

First, I wanted you, the reader, to explore real-world datasets and not randomly...

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Python for Data Analysis — A Critical Line-by-Line Review

book review pandas python Jul 09, 2019

In this post, I will offer my review of the book, Python for Data Analysis (2nd edition) by Wes McKinney. My name is Ted Petrou and I am an expert at pandas and author of the recently released Pandas Cookbook. I thoroughly read through PDA and created a very long, review that is available on github. This post provides some of the highlights from that full review.

What is a critical line-by-line review?

I read this book as if I was the only technical reviewer and I was counted on to find all the possible errors. Every single line of code was scrutinized and explored to see if a better solution existed. Having spent nearly every day of the last 18 months writing and talking about pandas, I have formed strong opinions about how it should be used. This critical examination lead to me finding fault with quite a large percentage of the code.

Review Focuses on Pandas

The main focus of PDA is on the pandas library but it does have material on basic Python, IPython...

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Selecting Subsets of Data in Pandas: Part 4

pandas Jun 30, 2019

This article is available as a Jupyter Notebook complete with exercises at the bottom to practice and detailed solutions in another notebook. All material will be contained in my Learn-Pandas Github repository.

This is the fourth and final part of the series “How to Select Subsets of Data in Pandas”. Pandas offers a wide variety of options for subset selection, which necessitates multiple articles. This series is broken down into the following topics.

  1. Selection with [].loc and .iloc
  2. Boolean indexing
  3. Assigning subsets of data
  4. How NOT to select subsets of data

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