`Pandas` DataFrames - Answer Key

Authors

Noor Sohail

Will Gammerdinger

Published

March 15, 2026

Exercise 1

Use the tail() method to inspect our metadata DataFrame.

metadata.tail()

	genotype	celltype	replicate
sample8	Wt	typeB	2
sample9	Wt	typeB	3
sample10	KO	typeB	1
sample11	KO	typeB	2
sample12	KO	typeB	3

Exercise 2

Retrieve the values of metadata where the value in the replicate is column is two or greater.

# Retrieve the columns of metadata where replicate is 2 or greater
metadata[metadata["replicate"] >= 2]

	genotype	celltype	replicate
sample2	Wt	typeA	2
sample3	Wt	typeA	3
sample5	KO	typeA	2
sample6	KO	typeA	3
sample8	Wt	typeB	2
sample9	Wt	typeB	3
sample11	KO	typeB	2
sample12	KO	typeB	3

Retrieve the values of metadata where the value in the genotype is not equal to Wt.

# Retrieve the columns of metadata where genotype is not 'Wt'
metadata[metadata["genotype"] != 'Wt']

	genotype	celltype	replicate
sample4	KO	typeA	1
sample5	KO	typeA	2
sample6	KO	typeA	3
sample10	KO	typeB	1
sample11	KO	typeB	2
sample12	KO	typeB	3

Exercise 3

Use the value_counts() method to summarize the number of times you observe each replicate number in the replicate column of metadata.

# Summarize the number of times we observe each replicate in metadata
metadata["replicate"].value_counts()

replicate
1    4
2    4
3    4
Name: count, dtype: int64

Reuse

CC-BY-4.0

---
title: "`Pandas` DataFrames - Answer Key"
author:
  - Noor Sohail
  - Will Gammerdinger
date: "2026-03-15"
license: "CC-BY-4.0"
editor_options: 
  markdown: 
    wrap: 72
jupyter: intro_python
---

```{python}
#| label: load_libraries_data_py
#| echo: false
# Load libraries and data
import pandas as pd
metadata = pd.read_csv("data/mouse_exp_design.csv")
```

# Exercise 1

1. Use the `tail()` method to inspect our `metadata` DataFrame.

```{python}
#| label: exercise_1
metadata.tail()
```


# Exercise 2

1. Retrieve the values of `metadata` where the value in the `replicate` is column is two or greater.

```{python}
#| label: metadata_replicate
# Retrieve the columns of metadata where replicate is 2 or greater
metadata[metadata["replicate"] >= 2]
```

2. Retrieve the values of `metadata` where the value in the `genotype` is not equal to `Wt`.

```{python}
#| label: metadata_genotype
# Retrieve the columns of metadata where genotype is not 'Wt'
metadata[metadata["genotype"] != 'Wt']
```

# Exercise 3

1. Use the `value_counts()` method to summarize the number of times you observe each replicate number in the `replicate` column of `metadata`.

```{python}
#| label: value_counts
# Summarize the number of times we observe each replicate in metadata
metadata["replicate"].value_counts()
```