Strings and bytes ​

Strings ​

In SmartPy strings are of type sp.string. Characters are restricted to the printable subset of 7-bit ASCII.

String literals are written in quotes, e.g. "abc" is a literal of type sp.string.

Both strings and bytes can be concatenated with +, e.g. "ab" + "c" == "abc".

sp.slice(offset: sp.nat, length: sp.nat, s: sp.string)
  -> sp.option[sp.string]

Extracts a substring from s, starting at offset (0 referring to the first character) and of length length. If the result is in bounds, the result will be wrapped in sp.Some, otherwise None is returned.

For example sp.slice(3,5,"0123456789") == sp.Some("34567") and sp.slice(3,5,"01234") == None.

sp.concat(xs: sp.list[sp.string]) -> sp.string

sp.concat concatenates a list of strings, for example:

assert sp.concat(["ab","cd","ef"]) == "abcdef"

Bytes ​

The type sp.bytes represents sequences of bytes.

Byte literals are written in hexadecimal notation: sp.bytes("0x100a") refers to a two-byte sequence.

sp.slice(offset: sp.nat, length: sp.nat, s: sp.bytes)
  -> sp.option[sp.bytes]

Extracts a subsequence of bytes from s, starting at offset (0 referring to the first character) and of length length. If the result is in bounds, the result will be wrapped in sp.Some, otherwise None is returned.

For example sp.slice(3,5,sp.bytes("0x00010203040506070809")) == sp.Some(sp.bytes("0x0304050607")) and sp.slice(3,5,sp.bytes("0x0001020304")) == None.

sp.concat(xs: sp.list[sp.bytes]) -> sp.bytes

sp.concat concatenates a list of sp.bytes, for example:

assert sp.concat([sp.bytes("0xab"), sp.bytes("0xcd")]) == sp.bytes("0xabcd")

Packing and unpacking ​

Most Michelson values can be packed and unpacked, i.e. converted to a sp.bytes representation.

sp.pack(x: t) : sp.bytes

Packs a value, i.e. obtains its sp.bytes representation.

The type t must be packable, which means that it doesn't involve big maps, operations, sapling states, or tickets.

sp.unpack(x: sp.bytes, t) -> sp.option[t]

Unpacks the sp.bytes representation x, assuming it represents a value of type t. Returns None if x does not represent a value of type t.