Many examples of dtype lines in the numpy documentation have a leading character | for example, '|S10' at the top of the structured arrays page in but not the structured arrays page and a link to data type objects seem to explain what that | means. What does | in this context and where is it documented?
|
'|S10'
It refers to byteorder / endianness in dtype. In particular, '|' indicates that the byte order is not applicable, for example, with 8-bit numbers.