How to get the width of a string in pixels?

I am using wxPython's HyperTreeList and I want to set the column width exactly equal to length of the largest string in it.

To accomplish that, I'd like to to convert a python string size into pixels.

For Example: If we have a string like

str = "python"
len(str) = 6

How could I convert the above string length/size into pixels?

Is there another way?