## Residue.num — PDB-style residue number

> This is the number of the residue, as used in PDB. (Not available for alignment sequences.)

> Note that the PDB residue number is stored as a 5-character string (not an integer). Conventionally, the first four characters are a sequence number, and an optional fifth character is the insertion code. For example, both `'1'` and `'1A'` are valid residue numbers, but a Python integer (without quotes) is not. Residue numbers longer than 5 characters will be truncated on assignment.

Example: See Residue.index command.