Feature	Solidity	Vyper
Version	$ solc --versionVersion: 0.6.12	$ vyper --version0.2.3
General notes on syntax	Solidity loosely borrows its syntax from Javascript and C	Vyper syntax is valid Python 3 syntax (but the opposite is not true)
Block delimiters	{ }	: # Vyper uses Python's off-side rule
Statement separator	;	\n' and :
End of line comment	// comment	# comment
Multiple line comment	/* multiple linecomment */	# Multiple line# comment
Constant	uint constant TOTAL_SUPPLY = 10000000;	TOTAL_SUPPLY: constant(uint256) = 10000000
Assignment	v = 1;	v = 1
Parallel assignment	(x, y) = (0, 1);	Tuple to tuple assignment not supported
Swap	(x, y) = (y, x);
Compound assignment	-=, *=, /=, %=, |=, &=, ^=	-=, *=, /=, %=, |=, &=, ^=
Increment and decrement	i++, ++i, i--, --i	i += 1, i -= 1
Null	null doesn't exist in Solidity but any unitialized variables take a default value represented by 0 in memory	null doesn't exist in Vyper but any unitialized variables take a default value represented by 0 in memory
Set variable to default value	delete v // doesn't work with mappings	v = empty(uint256)
Null test	v == 0	v == 0
Conditional expression	x > 0 ? x : -x	Conditional expression not supported
Contract lifecycle
Feature	Solidity	Vyper
Contract creation	Contract c = new Contract(args);
Contract creation with funding	Contract c = new Contract{value: amount}(args);
Salted contract creation (CREATE2)	Contract c = new Contract{salt: salt}(args);
Create forwarder contract		contract: address = create_forwarder_to(other_contract, value)
Selfdestruct (Avoid)	selfdestruct(refundAddr)	selfdestruct(refund_addr)
Interfaces
Feature	Solidity	Vyper
Interfaces	interface HelloWorld { function hello() external pure; function world(int) external pure;}	interface HelloWorld: def hello(): nonpayable def world(uint256): nonpayable
Interface type	interface HelloWorldWithEvent { event Event(); function hello() external pure; function world(int) external pure;}contract Test { bytes4 public hello_world_with_event = type(HelloWorldWithEvent).interfaceId;}
Operators
Feature	Solidity	Vyper
True and false	true false	True False
Falsehoods	FALSE	FALSE
Logical operators	&& || !	and or not
Relational operators	#ERROR!	#ERROR!
Min and max		max(x, y)
Arithmetic operators	#ERROR!	#ERROR!
Integer division	/	/
Bit operators	<< >> & | ^ ~	<< >> & | ^ ~
Binary & hex literals	uint x = 0x52string memory s = hex"52"	a: address= 0x14d465376c051Cbcd80Aa2d35Fd5df9910f80543b: Bytes[32]= b'\x01\x02\x03\x04\x05\x06... (32 bytes)d: Bytes[1] = 0b00010001
Data structures
Feature	Solidity	Vyper
String type	string	String[N] # N is a fixed number
Bytes type	bytes // dynamicbytes1, bytes2, ..., bytes32 // packedbytes[N] // N is a fixed number, unpacked	Bytes[N] # N is a fixed number
String literal	"don't \"no\""'don"t \'no\''�	"don't \"no\""'don"t \'no\''
String length	bytes(s).length	len(s)
String literal escapes	\ (escapes an actual newline)\\ (backslash)\' (single quote)\" (double quote)\b (backspace)\f (form feed)\n (newline)\r (carriage return)\t (tab)\v (vertical tab)\xNN (hex escape)\uNNNN (unicode escape)	\ (escapes an actual newline)\\ (backslash)\' (single quote)\" (double quote)\a (bell)\b (backspace)\f (form feed)\n (newline)\r (carriage return)\t (tab)\v (vertical tab)\ooo (octal escape)\xNN (hex escape)\uNNNN (unicode escape)\uNNNNNNNN (unicode escape)
Are strings mutable?	Yes	Yes
Slice	abi.decode(_payload[:4], (bytes4))// array slices only implemented for calldata arrays	slice(x, _start, _len)
String comparison	keccak256(abi.encodePacked(s1)) == keccak256(abi.encodePacked(s2))	keccak256(s1) == keccak256(s2)
String concatenation	abi.encodePacked(s1, s2)	concat(s1, s2)
Array literal	[1, 2, 3]	[1, 2, 3]
Length	a.length	len(a)
Empty test	a.length == 0
Lookup	a[0]	a[0]
Update	a[0] = 1;	a[0] = 1
Out of bounds access	Failing assertion	Failing assertion
Add new element	a.push(3); # Dynamic arrays
Remove element	a.pop(); # Dynamic arrays
Struct	struct Pair { uint x; uint y;} // Creating a structPair memory pair = Pair(2, 3); // Instantiating a struct variablerequire(pair.y > pair.x); // Accessing elements	struct Pair: x: uint256 y: uint256 # Creating a structpair: Pair = Pair({x: 2, y: 3}) # Instantiating a struct variableassert pair.y > pair.x # Accessing elements
Mapping size	Impossible to know	Impossible to know
Lookup	m[2]	m[2]
Update	m[2] = 1;	m[2] = 1
Missing key behaviour	A mapping has no concept of set keys, a mapping always refers to a hashed value that is the same for a given mapping and key	A mapping has no concept of set keys, a mapping always refers to a hashed value that is the same for a given mapping and key
Delete key	m[2] = 0;	m[2] = empty(uint256)
Immutable variables	uint immutable x; // have to be assigned in the constructor
Functions
Feature	Solidity	Vyper
Define function	function add2(uint x, uint y) public pure returns (uint) { return x + y;}	@externaldef add2(x: uint256, y: uint256) -> uint256: return x + y
Function argument storage location	function first(uint[] calldata x) public pure returns (uint) { // this function doesn't copy x to memory return x[0];}function first(uint[] memory x) public pure returns (uint) { // this function first copies x to memory return x[0];}
Invoke function	add2(x, y)	add2(x, y)
External function calls	c.f{gas: 1000, value: 4 ether}()	c.f()raw_call(address, data, outsize, gas, value, is_delegate_call)
Control flow
Feature	Solidity	Vyper
If statement	if (a > 2) { ...else if (a == 0) { ...} else { ...}	if a > 2: ...elif a == 0: ...else: ...
For loop	for (uint i = 0; i < 3; i++) { ...}	for i in range(3): ...
While loop	while (a > 0) { ...}
Do-While loop	do { ...} while (a > 0);
Return value	return x + y;	return x + y
Break	break;	break
Continue	continue;	continue
Assert	assert(x > y);	assert x > y
Require	require(x > y);
Revert	require(false, "revert reason")	raise "revert reason"
Exception handling	interface DataFeed { function getData(address token) external returns (uint value); }contract FeedConsumer { DataFeed feed; uint errorCount; function rate(address token) public returns (uint value, bool success) { // Permanently disable the mechanism if there are // more than 10 errors. require(errorCount < 10); try feed.getData(token) returns (uint v) { return (v, true); } catch Error(string memory /*reason*/) { // This is executed in case // revert was called inside getData // and a reason string was provided. errorCount++; return (0, false); } catch (bytes memory /*lowLevelData*/) { // This is executed in case revert() was used // or there was a failing assertion, division // by zero, etc. inside getData. errorCount++; return (0, false); } }}
Misc
Feature	Solidity	Vyper
Comments	NatSpec conventions for functions:/// @author Mary A. Botanist/// @notice Calculate tree age in years, rounded up, for live trees/// @dev The Alexandr N. Tetearing algorithm could increase precision/// @param rings The number of rings from dendrochronological sample/// @return age in years, rounded up for partial yearsEvents:/// The address `participant` just registered for the gathering.event Registered(address participant);Special inheritance syntax for contracts:/// @inheritdoc OtherContract	def foo(): """ @author Mary A. Botanist @notice Calculate tree age in years, rounded up, for live trees @dev The Alexandr N. Tetearing algorithm could increase precision @param rings The number of rings from dendrochronological sample @return age in years, rounded up for partial years """ ...
Payment with error on failure (Avoid for Solidity)	address.transfer()	send(address, value)
Payment with false on failure (Avoid for Solidity)	address.send()
Payment with gas forwarding (WARNING)	address.call.value().gas()()	raw_call(address, data, outsize, gas, value, is_delegate_call)
Event logging	event Deposit( address indexed _from, bytes32 indexed _id, uint _value);emit Deposit(msg.sender, _id, msg.value);	event Deposit: _from: indexed(address) _id: indexed(bytes32) _value: uint256log Deposit(msg.sender, _id, msg.value)
Units, global constants and type ranges	1 ether1 finney1 szabo1 wei1 gwei1 seconds1 minutes1 hours1 days1 weeks1 years // deprecatedtype(uint).mintype(uint).maxtype(int8).mintype(int8).max...	ZERO_ADDRESSas_wei_value(1, "finney")as_wei_value(1, "szabo")as_wei_value(1, "wei")as_wei_value(1, "babbage")as_wei_value(1, "shannon")EMPTY_BYTES32MAX_INT128MIN_INT128MAX_DECIMALMIN_DECIMALMAX_UINT256ZERO_WEI
Block and transaction properties	blockhash(blockNumber)block.coinbaseblock.difficultyblock.gaslimitblock.numberblock.timestampnow // alias for block.timestampgasleft()msg.datamsg.gasmsg.sendermsg.sigmsg.valuetx.gaspricetx.origin	blockhash(blockNumber)block.coinbaseblock.difficultyblock.numberblock.prevhash # Same as blockhash(block.number - 1)block.timestampmsg.gasmsg.sendermsg.valuetx.origin