Conditional Statements

Vyper uses the if , elif, and else statements to control flow for conditional logic.

Conditions are evaluated from left-to-right, an expression at a time, until the logic is found to be true or false.

# pragma version 0.4.0

# Notice that the syntax for defining `bool` output must have the words "True" or "False" start with first letter capitalised
@external
@pure
def check_less_than_ten(x: uint256) -> bool:
    if (x < 10):
        return True
    else:
        return False

@external
@pure
def check_multiple_conditions(y: uint256) -> uint256:
    if (y < 5):
        return 1
    elif (y == 5):
        return 2
    else:
        return 3

@external
@pure
def ternary_syntax(z: uint256) -> bool:
    return True if z < 5 else False

Vyper Differentiators

Vyper ternary operators start with defining the truthy output, then condition logic, and followed by falsy output. It does not use ? and : operator.

Conditional Statements

Further Reading: