Generating a dummy dataset

In this section, you will generate a dummy dataset.

Exit the sandbox

Exit the sandbox and return to the terminal.

>>> quit()

Generate a dummy dataset

In the terminal, type

opensafely exec ehrql:v0 generate-dataset dataset_definition.py

and press Enter.

The terminal will fill with a dummy dataset in CSV format. Scroll up to see the column headers; notice that two column headers correspond to the two columns — asthma_med_date and asthma_med_code — that you added to the dataset definition.

Also notice the lines that start with [info]. These show that the dummy data generator generated dummy data for 5,000 patients; found 500 that matched the dataset definition; and displayed them in the terminal.

The anatomy of an OpenSAFELY command

What do the parts of the OpenSAFELY command opensafely exec ehrql:v0 generate-dataset dataset_definition.py do?

• opensafely exec executes an OpenSAFELY action outside the project pipeline
• ehrql is the OpenSAFELY action to execute
• v0 is the major version of the ehrQL action
• generate-dataset is the ehrQL command to generate a dataset from a dataset definition
• dataset_definition.py is the dataset definition