An update just for johnno 
https://naalaa.com/n7/N7_221027.zip
Use 'str(x[, int_digits[, dec_digits]])' to format the returned string representation of x. int_digits is the minimum number of digits for the integer part (the string is padded with zeros), and dec_digits is the minimum number of digits for the decimal part.
Release notes
2022-10-27
* Added optional formatting parameters to 'str'

https://naalaa.com/n7/N7_221027.zip
Use 'str(x[, int_digits[, dec_digits]])' to format the returned string representation of x. int_digits is the minimum number of digits for the integer part (the string is padded with zeros), and dec_digits is the minimum number of digits for the decimal part.
Release notes
2022-10-27
* Added optional formatting parameters to 'str'