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:

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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:

smartpy

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

Bitwise logic ​

As of the Mumbai protocol upgrade bitwise and, or and xor operations are available as sp.and_bytes, sp.or_bytes and sp.xor_bytes on sp.bytes:

sp.and_bytes(x: sp.bytes, y: sp.bytes) → sp.bytes

sp.or_bytes(x: sp.bytes, y: sp.bytes) → sp.bytes

sp.xor_bytes(x: sp.bytes, y: sp.bytes) → sp.bytes

Performs the bitwise logical operations "and", "or", and "xor", respectively, on the arguments x and y, for example:

smartpy

assert sp.and_bytes(sp.bytes("0x2a"), sp.bytes("0x01")) == sp.bytes("0x00")
assert sp.or_bytes(sp.bytes("0x2a"), sp.bytes("0x01")) == sp.bytes("0x2b")
assert sp.xor_bytes(sp.bytes("0x2a"), sp.bytes("0x01")) == sp.bytes("0x2b")

sp.invert_bytes(x: sp.bytes) → sp.bytes

Computes the two's complement of x.

Shifting ​

Left and right shifts are also available as sp.lshift_bytes and sp.rshift_bytes on sp.bytes:

sp.lshift_bytes(x: sp.bytes, n: sp.nat) → sp.bytes

sp.lshift_bytes shifts x to the left by a given amount n, for example:

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assert sp.lshift_bytes(sp.bytes("0x2a"), sp.bytes("0x01")) == sp.bytes("0x54")

sp.rshift_bytes(x: sp.bytes, n: sp.nat) → sp.bytes

sp.rshift_bytes shifts x to the right by a given amount n, for example:

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assert sp.rshift_bytes(sp.bytes("0x2a"), sp.bytes("0x01")) == sp.bytes("0x15")

Packing and unpacking ​

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

sp.pack(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.