# Data handling tips

## Phone numbers in CSVs

Cells and columns in CSV don't have well-defined types so programs reading those CSVs generally infer the type from the values.

This can be a problem when opening a file with phone numbers which often start with a zero, and look like a number to programs reading CSVs.

When reading a CSV file, see if you can specify that such columns should be read as Text rather than letting the program infer the type.

![Example reading a CSV with the first phone number changed to text but the second will still be inferred from the data](https://3025923471-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M02trgcnmNckA-WvFeq%2F-Mi1do-VzK3VYIpeZ_vG%2F-Mi1ep-XnsUA-vlJPv1j%2FScreenshot_2021-08-26_15-29-47.png?alt=media\&token=7d4371dd-ffb4-40b9-9b6b-8cc8bec35127)

After reading, if the columns were read as text, the zero-prefixes will remain. If the program read it as numbers, the zero prefix will have been lost.

To check that the file was saved correctly, you can open it in a text editor like Notepad to check that the zeros are still there:

![Small part of a CSV shown in a text editor with phone number cells highlighted, correctly maintaining their zero prefixes.](https://3025923471-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M02trgcnmNckA-WvFeq%2F-Mi1ez-q0hDzXUu3WoK0%2F-Mi1fSxM6fqnM9zulJqM%2FScreenshot_2021-08-26_15-37-06.png?alt=media\&token=35dc0547-fcf8-4fd2-8c61-cbe308a36e2f)