Built-in Functions

Vyper provides a collection of built-in functions available in the global namespace of all contracts.

Bitwise Operations

bitwise_and(x: uint256, y: uint256) uint256

Perform a “bitwise and” operation. Each bit of the output is 1 if the corresponding bit of x AND of y is 1, otherwise it is 0.

@external
@view
def foo(x: uint256, y: uint256) -> uint256:
    return bitwise_and(x, y)
>>> ExampleContract.foo(31337, 8008135)
12353

Note

This function has been deprecated from version 0.3.4 onwards. Please use the & operator instead.

bitwise_not(x: uint256) uint256

Return the bitwise complement of x - the number you get by switching each 1 for a 0 and each 0 for a 1.

@external
@view
def foo(x: uint256) -> uint256:
    return bitwise_not(x)
>>> ExampleContract.foo(0)
115792089237316195423570985008687907853269984665640564039457584007913129639935

Note

This function has been deprecated from version 0.3.4 onwards. Please use the ~ operator instead.

bitwise_or(x: uint256, y: uint256) uint256

Perform a “bitwise or” operation. Each bit of the output is 0 if the corresponding bit of x AND of y is 0, otherwise it is 1.

@external
@view
def foo(x: uint256, y: uint256) -> uint256:
    return bitwise_or(x, y)
>>> ExampleContract.foo(31337, 8008135)
8027119

Note

This function has been deprecated from version 0.3.4 onwards. Please use the | operator instead.

bitwise_xor(x: uint256, y: uint256) uint256

Perform a “bitwise exclusive or” operation. Each bit of the output is the same as the corresponding bit in x if that bit in y is 0, and it is the complement of the bit in x if that bit in y is 1.

@external
@view
def foo(x: uint256, y: uint256) -> uint256:
    return bitwise_xor(x, y)
>>> ExampleContract.foo(31337, 8008135)
8014766

Note

This function has been deprecated from version 0.3.4 onwards. Please use the ^ operator instead.

shift(x: uint256, _shift: int128) uint256

Return x with the bits shifted _shift places. A positive _shift value equals a left shift, a negative value is a right shift.

@external
@view
def foo(x: uint256, y: int128) -> uint256:
    return shift(x, y)
>>> ExampleContract.foo(2, 8)
512

Chain Interaction

Vyper has three built-ins for contract creation; all three contract creation built-ins rely on the code to deploy already being stored on-chain, but differ in call vs deploy overhead, and whether or not they invoke the constructor of the contract to be deployed. The following list provides a short summary of the differences between them.

  • create_minimal_proxy_to(target: address, ...)
    • Creates an immutable proxy to target

    • Expensive to call (incurs a single DELEGATECALL overhead on every invocation), cheap to create (since it only deploys EIP-1167 forwarder bytecode)

    • Does not have the ability to call a constructor

    • Does not check that there is code at target (allows one to deploy proxies counterfactually)

  • create_copy_of(target: address, ...)
    • Creates a byte-for-byte copy of runtime code stored at target

    • Cheap to call (no DELEGATECALL overhead), expensive to create (200 gas per deployed byte)

    • Does not have the ability to call a constructor

    • Performs an EXTCODESIZE check to check there is code at target

  • create_from_blueprint(target: address, ...)
    • Deploys a contract using the initcode stored at target

    • Cheap to call (no DELEGATECALL overhead), expensive to create (200 gas per deployed byte)

    • Invokes constructor, requires a special “blueprint” contract to be deployed

    • Performs an EXTCODESIZE check to check there is code at target

create_minimal_proxy_to(target: address, value: uint256 = 0[, salt: bytes32]) address

Deploys a small, EIP1167-compliant “minimal proxy contract” that duplicates the logic of the contract at target, but has its own state since every call to target is made using DELEGATECALL to target. To the end user, this should be indistinguishable from an independently deployed contract with the same code as target.

  • target: Address of the contract to proxy to

  • value: The wei value to send to the new contract address (Optional, default 0)

  • salt: A bytes32 value utilized by the deterministic CREATE2 opcode (Optional, if not supplied, CREATE is used)

Returns the address of the newly created proxy contract. If the create operation fails (for instance, in the case of a CREATE2 collision), execution will revert.

@external
def foo(target: address) -> address:
    return create_minimal_proxy_to(target)

Note

It is very important that the deployed contract at target is code you know and trust, and does not implement the selfdestruct opcode or have upgradeable code as this will affect the operation of the proxy contract.

Note

There is no runtime check that there is code already deployed at target (since a proxy may be deployed counterfactually). Most applications may want to insert this check.

Note

Before version 0.3.4, this function was named create_forwarder_to.

create_copy_of(target: address, value: uint256 = 0[, salt: bytes32]) address

Create a physical copy of the runtime code at target. The code at target is byte-for-byte copied into a newly deployed contract.

  • target: Address of the contract to copy

  • value: The wei value to send to the new contract address (Optional, default 0)

  • salt: A bytes32 value utilized by the deterministic CREATE2 opcode (Optional, if not supplied, CREATE is used)

Returns the address of the created contract. If the create operation fails (for instance, in the case of a CREATE2 collision), execution will revert. If there is no code at target, execution will revert.

@external
def foo(target: address) -> address:
    return create_copy_of(target)

Note

The implementation of create_copy_of assumes that the code at target is smaller than 16MB. While this is much larger than the EIP-170 constraint of 24KB, it is a conservative size limit intended to future-proof deployer contracts in case the EIP-170 constraint is lifted. If the code at target is larger than 16MB, the behavior of create_copy_of is undefined.

create_from_blueprint(target: address, *args, value: uint256 = 0, code_offset=0[, salt: bytes32]) address

Copy the code of target into memory and execute it as initcode. In other words, this operation interprets the code at target not as regular runtime code, but directly as initcode. The *args are interpreted as constructor arguments, and are ABI-encoded and included when executing the initcode.

  • target: Address of the blueprint to invoke

  • *args: Constructor arguments to forward to the initcode.

  • value: The wei value to send to the new contract address (Optional, default 0)

  • code_offset: The offset to start the EXTCODECOPY from (Optional, default 0)

  • salt: A bytes32 value utilized by the deterministic CREATE2 opcode (Optional, if not supplied, CREATE is used)

Returns the address of the created contract. If the create operation fails (for instance, in the case of a CREATE2 collision), execution will revert. If code_offset >= target.codesize (ex. if there is no code at target), execution will revert.

@external
def foo(blueprint: address) -> address:
    arg1: uint256 = 18
    arg2: String = "some string"
    return create_from_blueprint(blueprint, arg1, arg2, code_offset=1)

Note

To properly deploy a blueprint contract, special deploy bytecode must be used. Deploying blueprint contracts is generally out of scope of this article, but the following preamble, prepended to regular deploy bytecode (output of vyper -f bytecode), should deploy the blueprint in an ordinary contract creation transaction: deploy_preamble = "61" + <bytecode len in 4 hex characters> + "3d81600a3d39f3". To see an example of this, please see the setup code for testing create_from_blueprint.

Warning

It is recommended to deploy blueprints with the ERC5202 preamble 0xfe7100 to guard them from being called as regular contracts. This is particularly important for factories where the constructor has side effects (including SELFDESTRUCT!), as those could get executed by anybody calling the blueprint contract directly. The code_offset= kwarg is provided to enable this pattern:

@external
def foo(blueprint: address) -> address:
    # `blueprint` is a blueprint contract with some known preamble b"abcd..."
    return create_from_blueprint(blueprint, code_offset=<preamble length>)
raw_call(to: address, data: Bytes, max_outsize: int = 0, gas: uint256 = gasLeft, value: uint256 = 0, is_delegate_call: bool = False, is_static_call: bool = False, revert_on_failure: bool = True) Bytes[max_outsize]

Call to the specified Ethereum address.

  • to: Destination address to call to

  • data: Data to send to the destination address

  • max_outsize: Maximum length of the bytes array returned from the call. If the returned call data exceeds this length, only this number of bytes is returned.

  • gas: The amount of gas to attach to the call. If not set, all remaining gas is forwarded.

  • value: The wei value to send to the address (Optional, default 0)

  • is_delegate_call: If True, the call will be sent as DELEGATECALL (Optional, default False)

  • is_static_call: If True, the call will be sent as STATICCALL (Optional, default False)

  • revert_on_failure: If True, the call will revert on a failure, otherwise success will be returned (Optional, default True)

Note

Returns the data returned by the call as a Bytes list, with max_outsize as the max length. The actual size of the returned data may be less than max_outsize. You can use len to obtain the actual size.

Returns nothing if max_outsize is omitted or set to 0.

Returns success in a tuple with return value if revert_on_failure is set to False.

@external
@payable
def foo(_target: address) -> Bytes[32]:
    response: Bytes[32] = raw_call(_target, method_id("someMethodName()"), max_outsize=32, value=msg.value)
    return response

@external
@payable
def bar(_target: address) -> Bytes[32]:
    success: bool = False
    response: Bytes[32] = b""
    x: uint256 = 123
    success, response = raw_call(
        _target,
        _abi_encode(x, method_id=method_id("someMethodName(uint256)")),
        max_outsize=32,
        value=msg.value,
        revert_on_failure=False
        )
    assert success
    return response
raw_log(topics: bytes32[4], data: Union[Bytes, bytes32]) None

Provides low level access to the LOG opcodes, emitting a log without having to specify an ABI type.

  • topics: List of bytes32 log topics. The length of this array determines which opcode is used.

  • data: Unindexed event data to include in the log. May be given as Bytes or bytes32.

@external
def foo(_topic: bytes32, _data: Bytes[100]):
    raw_log([_topic], _data)
raw_revert(data: Bytes) None

Provides low level access to the REVERT opcode, reverting execution with the specified data returned.

  • data: Data representing the error message causing the revert.

@external
def foo(_data: Bytes[100]):
    raw_revert(_data)
selfdestruct(to: address) None

Trigger the SELFDESTRUCT opcode (0xFF), causing the contract to be destroyed.

  • to: Address to forward the contract’s ether balance to

Warning

This method deletes the contract from the blockchain. All non-ether assets associated with this contract are “burned” and the contract is no longer accessible.

@external
def do_the_needful():
    selfdestruct(msg.sender)
send(to: address, value: uint256) None

Send ether from the contract to the specified Ethereum address.

  • to: The destination address to send ether to

  • value: The wei value to send to the address

Note

The amount to send is always specified in wei.

@external
def foo(_receiver: address, _amount: uint256):
    send(_receiver, _amount)

Cryptography

ecadd(a: uint256[2], b: uint256[2]) uint256[2]

Take two points on the Alt-BN128 curve and add them together.

@external
@view
def foo(x: uint256[2], y: uint256[2]) -> uint256[2]:
    return ecadd(x, y)
>>> ExampleContract.foo([1, 2], [1, 2])
[
    1368015179489954701390400359078579693043519447331113978918064868415326638035,
    9918110051302171585080402603319702774565515993150576347155970296011118125764,
]
ecmul(point: uint256[2], scalar: uint256) uint256[2]

Take a point on the Alt-BN128 curve (p) and a scalar value (s), and return the result of adding the point to itself s times, i.e. p * s.

  • point: Point to be multiplied

  • scalar: Scalar value

@external
@view
def foo(point: uint256[2], scalar: uint256) -> uint256[2]:
    return ecmul(point, scalar)
>>> ExampleContract.foo([1, 2], 3)
[
    3353031288059533942658390886683067124040920775575537747144343083137631628272,
    19321533766552368860946552437480515441416830039777911637913418824951667761761,
]
ecrecover(hash: bytes32, v: uint256 | uint8, r: uint256 | bytes32, s: uint256 | bytes32) address

Recover the address associated with the public key from the given elliptic curve signature.

  • r: first 32 bytes of signature

  • s: second 32 bytes of signature

  • v: final 1 byte of signature

Returns the associated address, or 0 on error.

@external
@view
def foo(hash: bytes32, v: uint8, r:bytes32, s:bytes32) -> address:
    return ecrecover(hash, v, r, s)


@external
@view
def foo(hash: bytes32, v: uint256, r:uint256, s:uint256) -> address:
    return ecrecover(hash, v, r, s)
>>> ExampleContract.foo('0x6c9c5e133b8aafb2ea74f524a5263495e7ae5701c7248805f7b511d973dc7055',
     28,
     78616903610408968922803823221221116251138855211764625814919875002740131251724,
     37668412420813231458864536126575229553064045345107737433087067088194345044408
    )
'0x9eE53ad38Bb67d745223a4257D7d48cE973FeB7A'
keccak256(_value) bytes32

Return a keccak256 hash of the given value.

  • _value: Value to hash. Can be a literal string, Bytes, or bytes32.

@external
@view
def foo(_value: Bytes[100]) -> bytes32
    return keccak256(_value)
>>> ExampleContract.foo(b"potato")
0x9e159dfcfe557cc1ca6c716e87af98fdcb94cd8c832386d0429b2b7bec02754f
sha256(_value) bytes32

Return a sha256 (SHA2 256-bit output) hash of the given value.

  • _value: Value to hash. Can be a literal string, Bytes, or bytes32.

@external
@view
def foo(_value: Bytes[100]) -> bytes32
    return sha256(_value)
>>> ExampleContract.foo(b"potato")
0xe91c254ad58860a02c788dfb5c1a65d6a8846ab1dc649631c7db16fef4af2dec

Data Manipulation

concat(a, b, *args) Union[Bytes, String]

Take 2 or more bytes arrays of type bytes32, Bytes or String and combine them into a single value.

If the input arguments are String the return type is String. Otherwise the return type is Bytes.

@external
@view
def foo(a: String[5], b: String[5], c: String[5]) -> String[100]:
    return concat(a, " ", b, " ", c, "!")
>>> ExampleContract.foo("why","hello","there")
"why hello there!"
convert(value, type_) Any

Converts a variable or literal from one type to another.

  • value: Value to convert

  • type_: The destination type to convert to (e.g., bool, decimal, int128, uint256 or bytes32)

Returns a value of the type specified by type_.

For more details on available type conversions, see Type Conversions.

uint2str(value: unsigned integer) String

Returns an unsigned integer’s string representation.

  • value: Unsigned integer to convert.

Returns the string representation of value.

@external
@view
def foo(b: uint256) -> String[78]:
    return uint2str(b)
>>> ExampleContract.foo(420)
"420"
extract32(b: Bytes, start: uint256, output_type=bytes32) Any

Extract a value from a Bytes list.

  • b: Bytes list to extract from

  • start: Start point to extract from

  • output_type: Type of output (bytes32, integer, or address). Defaults to bytes32.

Returns a value of the type specified by output_type.

@external
@view
def foo(b: Bytes[32]) -> address:
    return extract32(b, 0, output_type=address)
>>> ExampleContract.foo("0x0000000000000000000000009f8F72aA9304c8B593d555F12eF6589cC3A579A2")
"0x9f8F72aA9304c8B593d555F12eF6589cC3A579A2"
slice(b: Union[Bytes, bytes32, String], start: uint256, length: uint256) Union[Bytes, String]

Copy a list of bytes and return a specified slice.

  • b: value being sliced

  • start: start position of the slice

  • length: length of the slice

If the value being sliced is a Bytes or bytes32, the return type is Bytes. If it is a String, the return type is String.

@external
@view
def foo(s: String[32]) -> String[5]:
    return slice(s, 4, 5)
>>> ExampleContract.foo("why hello! how are you?")
"hello"

Math

abs(value: int256) int256

Return the absolute value of a signed integer.

  • value: Integer to return the absolute value of

@external
@view
def foo(value: int256) -> int256:
    return abs(value)
>>> ExampleContract.foo(-31337)
31337
ceil(value: decimal) int256

Round a decimal up to the nearest integer.

  • value: Decimal value to round up

@external
@view
def foo(x: decimal) -> int256:
    return ceil(x)
>>> ExampleContract.foo(3.1337)
4
floor(value: decimal) int256

Round a decimal down to the nearest integer.

  • value: Decimal value to round down

@external
@view
def foo(x: decimal) -> int256:
    return floor(x)
>>> ExampleContract.foo(3.1337)
3
max(a: numeric, b: numeric) numeric

Return the greater value of a and b. The input values may be any numeric type as long as they are both of the same type. The output value is of the same type as the input values.

@external
@view
def foo(a: uint256, b: uint256) -> uint256:
    return max(a, b)
>>> ExampleContract.foo(23, 42)
42
max_value(type_) numeric

Returns the maximum value of the numeric type specified by type_ (e.g., int128, uint256, decimal).

@external
@view
def foo() -> int256:
    return max_value(int256)
>>> ExampleContract.foo()
57896044618658097711785492504343953926634992332820282019728792003956564819967
min(a: numeric, b: numeric) numeric

Returns the lesser value of a and b. The input values may be any numeric type as long as they are both of the same type. The output value is of the same type as the input values.

@external
@view
def foo(a: uint256, b: uint256) -> uint256:
    return min(a, b)
>>> ExampleContract.foo(23, 42)
23
min_value(type_) numeric

Returns the minimum value of the numeric type specified by type_ (e.g., int128, uint256, decimal).

@external
@view
def foo() -> int256:
    return min_value(int256)
>>> ExampleContract.foo()
-57896044618658097711785492504343953926634992332820282019728792003956564819968
pow_mod256(a: uint256, b: uint256) uint256

Return the result of a ** b % (2 ** 256).

This method is used to perform exponentiation without overflow checks.

@external
@view
def foo(a: uint256, b: uint256) -> uint256:
    return pow_mod256(a, b)
>>> ExampleContract.foo(2, 3)
8
>>> ExampleContract.foo(100, 100)
59041770658110225754900818312084884949620587934026984283048776718299468660736
sqrt(d: decimal) decimal

Return the square root of the provided decimal number, using the Babylonian square root algorithm.

@external
@view
def foo(d: decimal) -> decimal:
    return sqrt(d)
>>> ExampleContract.foo(9.0)
3.0
isqrt(x: uint256) uint256

Return the (integer) square root of the provided integer number, using the Babylonian square root algorithm. The rounding mode is to round down to the nearest integer. For instance, isqrt(101) == 10.

@external
@view
def foo(x: uint256) -> uint256:
    return isqrt(x)
>>> ExampleContract.foo(101)
10
uint256_addmod(a: uint256, b: uint256, c: uint256) uint256

Return the modulo of (a + b) % c. Reverts if c == 0.

@external
@view
def foo(a: uint256, b: uint256, c: uint256) -> uint256:
    return uint256_addmod(a, b, c)
>>> (6 + 13) % 8
3
>>> ExampleContract.foo(6, 13, 8)
3
uint256_mulmod(a: uint256, b: uint256, c: uint256) uint256

Return the modulo from (a * b) % c. Reverts if c == 0.

@external
@view
def foo(a: uint256, b: uint256, c: uint256) -> uint256:
    return uint256_mulmod(a, b, c)
>>> (11 * 2) % 5
2
>>> ExampleContract.foo(11, 2, 5)
2
unsafe_add(x: integer, y: integer) integer

Add x and y, without checking for overflow. x and y must both be integers of the same type. If the result exceeds the bounds of the input type, it will be wrapped.

@external
@view
def foo(x: uint8, y: uint8) -> uint8:
    return unsafe_add(x, y)

@external
@view
def bar(x: int8, y: int8) -> int8:
    return unsafe_add(x, y)
>>> ExampleContract.foo(1, 1)
2

>>> ExampleContract.foo(255, 255)
254

>>> ExampleContract.bar(127, 127)
-2

Note

Performance note: for the native word types of the EVM uint256 and int256, this will compile to a single ADD instruction, since the EVM natively wraps addition on 256-bit words.

unsafe_sub(x: integer, y: integer) integer

Subtract x and y, without checking for overflow. x and y must both be integers of the same type. If the result underflows the bounds of the input type, it will be wrapped.

@external
@view
def foo(x: uint8, y: uint8) -> uint8:
    return unsafe_sub(x, y)

@external
@view
def bar(x: int8, y: int8) -> int8:
    return unsafe_sub(x, y)
>>> ExampleContract.foo(4, 3)
1

>>> ExampleContract.foo(0, 1)
255

>>> ExampleContract.bar(-128, 1)
127

Note

Performance note: for the native word types of the EVM uint256 and int256, this will compile to a single SUB instruction, since the EVM natively wraps subtraction on 256-bit words.

unsafe_mul(x: integer, y: integer) integer

Multiply x and y, without checking for overflow. x and y must both be integers of the same type. If the result exceeds the bounds of the input type, it will be wrapped.

@external
@view
def foo(x: uint8, y: uint8) -> uint8:
    return unsafe_mul(x, y)

@external
@view
def bar(x: int8, y: int8) -> int8:
    return unsafe_mul(x, y)
>>> ExampleContract.foo(1, 1)
1

>>> ExampleContract.foo(255, 255)
1

>>> ExampleContract.bar(-128, -128)
0

>>> ExampleContract.bar(127, -128)
-128

Note

Performance note: for the native word types of the EVM uint256 and int256, this will compile to a single MUL instruction, since the EVM natively wraps multiplication on 256-bit words.

unsafe_div(x: integer, y: integer) integer

Divide x and y, without checking for division-by-zero. x and y must both be integers of the same type. If the denominator is zero, the result will (following EVM semantics) be zero.

@external
@view
def foo(x: uint8, y: uint8) -> uint8:
    return unsafe_div(x, y)

@external
@view
def bar(x: int8, y: int8) -> int8:
    return unsafe_div(x, y)
>>> ExampleContract.foo(1, 1)
1

>>> ExampleContract.foo(1, 0)
0

>>> ExampleContract.bar(-128, -1)
-128

Note

Performance note: this will compile to a single SDIV or DIV instruction, depending on if the inputs are signed or unsigned (respectively).

Utilities

as_wei_value(_value, unit: str) uint256

Take an amount of ether currency specified by a number and a unit and return the integer quantity of wei equivalent to that amount.

  • _value: Value for the ether unit. Any numeric type may be used, however the value cannot be negative.

  • unit: Ether unit name (e.g. "wei", "ether", "gwei", etc.) indicating the denomination of _value. Must be given as a literal string.

@external
@view
def foo(s: String[32]) -> uint256:
    return as_wei_value(1.337, "ether")
>>> ExampleContract.foo(1)
1337000000000000000
blockhash(block_num: uint256) bytes32

Return the hash of the block at the specified height.

Note

The EVM only provides access to the most recent 256 blocks. This function returns EMPTY_BYTES32 if the block number is greater than or equal to the current block number or more than 256 blocks behind the current block.

@external
@view
def foo() -> bytes32:
    return blockhash(block.number - 16)
>>> ExampleContract.foo()
0xf3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
empty(typename) Any

Return a value which is the default (zero-ed) value of its type. Useful for initializing new memory variables.

  • typename: Name of the type

@external
@view
def foo():
    x: uint256[2][5] = empty(uint256[2][5])
len(b: Union[Bytes, String]) uint256

Return the length of a given Bytes or String.

@external
@view
def foo(s: String[32]) -> uint256:
    return len(s)
>>> ExampleContract.foo("hello")
5
method_id(method, output_type: type = Bytes[4]) Union[Bytes[4], bytes4]

Takes a function declaration and returns its method_id (used in data field to call it).

  • method: Method declaration as given as a literal string

  • output_type: The type of output (Bytes[4] or bytes4). Defaults to Bytes[4].

Returns a value of the type specified by output_type.

@external
@view
def foo() -> Bytes[4]:
    return method_id('transfer(address,uint256)', output_type=Bytes[4])
>>> ExampleContract.foo()
0xa9059cbb
_abi_encode(*args, ensure_tuple: bool = True) Bytes[<depends on input>]

Takes a variable number of args as input, and returns the ABIv2-encoded bytestring. Used for packing arguments to raw_call, EIP712 and other cases where a consistent and efficient serialization method is needed. Once this function has seen more use we provisionally plan to put it into the ethereum.abi namespace.

  • *args: Arbitrary arguments

  • ensure_tuple: If set to True, ensures that even a single argument is encoded as a tuple. In other words, bytes gets encoded as (bytes,), and (bytes,) gets encoded as ((bytes,),) This is the calling convention for Vyper and Solidity functions. Except for very specific use cases, this should be set to True. Must be a literal.

  • method_id: A literal hex or Bytes[4] value to append to the beginning of the abi-encoded bytestring.

Returns a bytestring whose max length is determined by the arguments. For example, encoding a Bytes[32] results in a Bytes[64] (first word is the length of the bytestring variable).

@external
@view
def foo() -> Bytes[132]:
    x: uint256 = 1
    y: Bytes[32] = b"234"
    return _abi_encode(x, y, method_id=method_id("foo()"))
>>> ExampleContract.foo().hex()
"c2985578"
"0000000000000000000000000000000000000000000000000000000000000001"
"0000000000000000000000000000000000000000000000000000000000000040"
"0000000000000000000000000000000000000000000000000000000000000003"
"3233340000000000000000000000000000000000000000000000000000000000"
_abi_decode(b: Bytes, output_type: type_, unwrap_tuple: bool = True) Any

Takes a byte array as input, and returns the decoded values according to the specified output types. Used for unpacking ABIv2-encoded values. Once this function has seen more use we provisionally plan to put it into the ethereum.abi namespace.

  • b: A byte array of a length that is between the minimum and maximum ABIv2 size bounds of the output type.

  • output_type: Name of the output type, or tuple of output types, to be decoded.

  • unwrap_tuple: If set to True, the input is decoded as a tuple even if only one output type is specified. In other words, _abi_decode(b, Bytes[32]) gets decoded as (Bytes[32],). This is the convention for ABIv2-encoded values generated by Vyper and Solidity functions. Except for very specific use cases, this should be set to True. Must be a literal.

Returns the decoded value(s), with type as specified by output_type.

@external
@view
def foo(someInput: Bytes[128]) -> (uint256, Bytes[32]):
    x: uint256 = empty(uint256)
    y: Bytes[32] = empty(Bytes[32])
    x, y =  _abi_decode(someInput, (uint256, Bytes[32]))
    return x, y
print(*args, hardhat_compat=False) None

“prints” the arguments by issuing a static call to the “console” address, 0x000000000000000000636F6E736F6C652E6C6F67. This is supported by some smart contract development frameworks.

The default mode works natively with titanoboa. For hardhat-style frameworks, use hardhat_compat=True).

Note

Issuing of the static call is NOT mode-dependent (that is, it is not removed from production code), although the compiler will issue a warning whenever print is used.