last() method, no negative index lookups

test_libs/pyspec/eth2spec/test/helpers/custody.py

@@ -4,7 +4,7 @@ from eth2spec.utils.bls import bls_sign
 
 def get_valid_early_derived_secret_reveal(spec, state, epoch=None):
     current_epoch = spec.get_current_epoch(state)
-    revealed_index = spec.get_active_validator_indices(state, current_epoch)[-1]
+    revealed_index = spec.get_active_validator_indices(state, current_epoch).last()
     masker_index = spec.get_active_validator_indices(state, current_epoch)[0]
 
     if epoch is None:

test_libs/pyspec/eth2spec/test/helpers/proposer_slashings.py

@@ -6,7 +6,7 @@ from eth2spec.test.helpers.keys import pubkey_to_privkey
 
 def get_valid_proposer_slashing(spec, state, signed_1=False, signed_2=False):
     current_epoch = spec.get_current_epoch(state)
-    validator_index = spec.get_active_validator_indices(state, current_epoch)[-1]
+    validator_index = spec.get_active_validator_indices(state, current_epoch).last()
     privkey = pubkey_to_privkey[state.validators[validator_index].pubkey]
     slot = state.slot
 

test_libs/pyspec/eth2spec/test/helpers/transfers.py

@@ -9,7 +9,7 @@ def get_valid_transfer(spec, state, slot=None, sender_index=None, amount=None, f
         slot = state.slot
     current_epoch = spec.get_current_epoch(state)
     if sender_index is None:
-        sender_index = spec.get_active_validator_indices(state, current_epoch)[-1]
+        sender_index = spec.get_active_validator_indices(state, current_epoch).last()
     recipient_index = spec.get_active_validator_indices(state, current_epoch)[0]
     transfer_pubkey = pubkeys[-1]
     transfer_privkey = privkeys[-1]

test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_transfer.py

@@ -63,7 +63,7 @@ def test_success_withdrawable(spec, state):
 @with_all_phases
 @spec_state_test
 def test_success_active_above_max_effective(spec, state):
-    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     state.balances[sender_index] = spec.MAX_EFFECTIVE_BALANCE + 1
     transfer = get_valid_transfer(spec, state, sender_index=sender_index, amount=1, fee=0, signed=True)
 
@@ -73,7 +73,7 @@ def test_success_active_above_max_effective(spec, state):
 @with_all_phases
 @spec_state_test
 def test_success_active_above_max_effective_fee(spec, state):
-    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     state.balances[sender_index] = spec.MAX_EFFECTIVE_BALANCE + 1
     transfer = get_valid_transfer(spec, state, sender_index=sender_index, amount=0, fee=1, signed=True)
 
@@ -94,7 +94,7 @@ def test_invalid_signature(spec, state):
 @with_all_phases
 @spec_state_test
 def test_active_but_transfer_past_effective_balance(spec, state):
-    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     amount = spec.MAX_EFFECTIVE_BALANCE // 32
     state.balances[sender_index] = spec.MAX_EFFECTIVE_BALANCE
     transfer = get_valid_transfer(spec, state, sender_index=sender_index, amount=amount, fee=0, signed=True)
@@ -115,7 +115,7 @@ def test_incorrect_slot(spec, state):
 @with_all_phases
 @spec_state_test
 def test_insufficient_balance_for_fee(spec, state):
-    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     state.balances[sender_index] = spec.MAX_EFFECTIVE_BALANCE
     transfer = get_valid_transfer(spec, state, sender_index=sender_index, amount=0, fee=1, signed=True)
 
@@ -128,7 +128,7 @@ def test_insufficient_balance_for_fee(spec, state):
 @with_all_phases
 @spec_state_test
 def test_insufficient_balance(spec, state):
-    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     state.balances[sender_index] = spec.MAX_EFFECTIVE_BALANCE
     transfer = get_valid_transfer(spec, state, sender_index=sender_index, amount=1, fee=0, signed=True)
 
@@ -141,7 +141,7 @@ def test_insufficient_balance(spec, state):
 @with_all_phases
 @spec_state_test
 def test_no_dust_sender(spec, state):
-    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     balance = state.balances[sender_index]
     transfer = get_valid_transfer(
         spec,
@@ -161,7 +161,7 @@ def test_no_dust_sender(spec, state):
 @with_all_phases
 @spec_state_test
 def test_no_dust_recipient(spec, state):
-    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     state.balances[sender_index] = spec.MAX_EFFECTIVE_BALANCE + 1
     transfer = get_valid_transfer(spec, state, sender_index=sender_index, amount=1, fee=0, signed=True)
     state.balances[transfer.recipient] = 0

test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_voluntary_exit.py

@@ -93,7 +93,7 @@ def test_success_exit_queue(spec, state):
             continue
 
     # exit an additional validator
-    validator_index = spec.get_active_validator_indices(state, current_epoch)[-1]
+    validator_index = spec.get_active_validator_indices(state, current_epoch).last()
     privkey = pubkey_to_privkey[state.validators[validator_index].pubkey]
     voluntary_exit = build_voluntary_exit(
         spec,

test_libs/pyspec/eth2spec/test/sanity/test_blocks.py

@@ -269,7 +269,7 @@ def test_voluntary_exit(spec, state):
     validator_index = spec.get_active_validator_indices(
         state,
         spec.get_current_epoch(state)
-    )[-1]
+    ).last()
 
     # move state forward PERSISTENT_COMMITTEE_PERIOD epochs to allow for exit
     state.slot += spec.PERSISTENT_COMMITTEE_PERIOD * spec.SLOTS_PER_EPOCH
@@ -315,7 +315,7 @@ def test_voluntary_exit(spec, state):
     # overwrite default 0 to test
     # spec.MAX_TRANSFERS = 1
 
-    # sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state))[-1]
+    # sender_index = spec.get_active_validator_indices(state, spec.get_current_epoch(state)).last()
     # amount = get_balance(state, sender_index)
 
     # transfer = get_valid_transfer(spec, state, state.slot + 1, sender_index, amount, signed=True)
@@ -347,7 +347,7 @@ def test_voluntary_exit(spec, state):
 @spec_state_test
 def test_balance_driven_status_transitions(spec, state):
     current_epoch = spec.get_current_epoch(state)
-    validator_index = spec.get_active_validator_indices(state, current_epoch)[-1]
+    validator_index = spec.get_active_validator_indices(state, current_epoch).last()
 
     assert state.validators[validator_index].exit_epoch == spec.FAR_FUTURE_EPOCH
 

test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py

@@ -312,6 +312,10 @@ class BaseList(list, Elements):
     def __iter__(self) -> Iterator[SSZValue]:
         return super().__iter__()
 
+    def last(self):
+        # be explict about getting the last item, for the non-python readers, and negative-index safety
+        return self[len(self)-1]
+
 
 class List(BaseList):