Reading CSV files (read_csv) in Data Analysis Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the read_csv function in data analysis?

The read_csv function is used to load data from a CSV (Comma-Separated Values) file into a DataFrame, which is a table-like structure for easy data analysis.

beginner

How do you specify a different delimiter when reading a CSV file with read_csv?

You use the delimiter or sep parameter to tell read_csv what character separates the values, for example: pd.read_csv('file.csv', delimiter=';').

beginner

What does the header=None argument do in read_csv?

It tells read_csv that the CSV file has no header row, so pandas will assign default column names as numbers starting from 0.

intermediate

How can you read only specific columns from a CSV file using read_csv?

Use the usecols parameter with a list of column names or indices you want to load, for example: pd.read_csv('file.csv', usecols=['Name', 'Age']).

beginner

What happens if the CSV file contains missing values when using read_csv?

Pandas will automatically represent missing values as NaN (Not a Number), which you can later handle or clean in your analysis.

Which function is used to load data from a CSV file into a DataFrame?

A read_csv

B load_data

C import_csv

D open_csv

The correct function to read CSV files into a DataFrame is read_csv.

How do you tell read_csv that the file has no header row?

A header=None

B skip_header=True

C no_header=True

D header=0

Using header=None tells pandas the CSV file has no header row.

What parameter do you use to read only certain columns from a CSV file?

A columns

B select_cols

C usecols

D cols

The usecols parameter specifies which columns to load.

If your CSV uses semicolons instead of commas, which parameter should you change?

A header=';'

B separator=','

C sep=','

D delimiter=';'

Set delimiter=';' or sep=';' to read files with semicolon separators.

What does pandas use to represent missing values when reading CSV files?

A None

B NaN

C 0

D Empty string

Pandas uses NaN to represent missing values.

Explain how to load a CSV file that uses tabs as separators and has no header row.

Think about how to tell pandas about the separator and header.

Describe how you would load only the columns 'Name' and 'Age' from a CSV file using read_csv.

Focus on selecting specific columns during loading.