.. opcode:: EXTENDED_ARG (ext)
- Prefixes any opcode which has an argument too big to fit into the default two
- bytes. *ext* holds two additional bytes which, taken together with the
- subsequent opcode's argument, comprise a four-byte argument, *ext* being the
- two most-significant bytes.
+ Prefixes any opcode which has an argument too big to fit into the default one
+ byte. *ext* holds an additional byte which act as higher bits in the argument.
+ For each opcode, at most three prefixal ``EXTENDED_ARG`` are allowed, forming
+ an argument from two-byte to four-byte.
.. opcode:: FORMAT_VALUE (flags)