Back
Lesson 15:
Assertions and Exceptions
Introduction to Vyper assertions and exceptions
Progress: 0%
Visit desktop version for better experiences.
Assertions and Exceptions
Vyper uses state-reverting exceptions to handle errors. The code stops executing when an exception is triggered, and the state is reverted to before the transaction took place. The remaining gas is returned to the transaction sender.
Assert
Use assert statement to evaluate a condition. The transaction is reverted if the condition returns "False".
Assertion statements should be written as assert sample_logic < 5, "error_string".
Raise
raise statment reverts current call and triggers an exception.
Raise statements should be written as raise "error_string".
ℹ️ Note
While error strings are not required, it is recommended to be explicit with error messages to help with debugging.
# pragma version 0.4.0
sample_balance: public(uint256)
FIXED_CONSTANT: constant(uint256) = 100
@external
def deposit(amount: uint256):
assert amount > 10, "Amount must be greater than 0"
self.sample_balance += amount
@external
def check_amount(num: uint256):
if num > FIXED_CONSTANT:
raise "Amount exceeds fixed constant"
else:
self.sample_balance += numVyper Differentiators
- Vyper does not have
requirekeyword.