diff --git a/torba/torba/client/baseaccount.py b/torba/torba/client/baseaccount.py
index 8b9ff838c..4c7644fe6 100644
--- a/torba/torba/client/baseaccount.py
+++ b/torba/torba/client/baseaccount.py
@@ -85,7 +85,7 @@ class AddressManager:
 class HierarchicalDeterministic(AddressManager):
     """ Implements simple version of Bitcoin Hierarchical Deterministic key management. """
 
-    name = "deterministic-chain"
+    name: str = "deterministic-chain"
 
     __slots__ = 'gap', 'maximum_uses_per_address'
 
@@ -164,7 +164,7 @@ class HierarchicalDeterministic(AddressManager):
 class SingleKey(AddressManager):
     """ Single Key address manager always returns the same address for all operations. """
 
-    name = "single-address"
+    name: str = "single-address"
 
     __slots__ = ()
 
diff --git a/torba/torba/client/basedatabase.py b/torba/torba/client/basedatabase.py
index bb43150eb..d0dd07503 100644
--- a/torba/torba/client/basedatabase.py
+++ b/torba/torba/client/basedatabase.py
@@ -102,20 +102,20 @@ def constraints_to_sql(constraints, joiner=' AND ', prepend_key=''):
         if not key:
             sql.append(constraint)
             continue
-        elif key.startswith('$'):
+        if key.startswith('$'):
             values[key] = constraint
             continue
-        elif key.endswith('__not'):
+        if key.endswith('__not'):
             col, op = col[:-len('__not')], '!='
         elif key.endswith('__is_null'):
             col = col[:-len('__is_null')]
             sql.append(f'{col} IS NULL')
             continue
-        elif key.endswith('__is_not_null'):
+        if key.endswith('__is_not_null'):
             col = col[:-len('__is_not_null')]
             sql.append(f'{col} IS NOT NULL')
             continue
-        elif key.endswith('__lt'):
+        if key.endswith('__lt'):
             col, op = col[:-len('__lt')], '<'
         elif key.endswith('__lte'):
             col, op = col[:-len('__lte')], '<='
@@ -149,7 +149,7 @@ def constraints_to_sql(constraints, joiner=' AND ', prepend_key=''):
             sql.append(f'({where})')
             values.update(subvalues)
             continue
-        elif key.endswith('__and'):
+        if key.endswith('__and'):
             where, subvalues = constraints_to_sql(constraint, ' AND ', key+tag+'_')
             sql.append(f'({where})')
             values.update(subvalues)
@@ -554,7 +554,7 @@ class BaseDatabase(SQLiteMixin):
                         row[1], height=row[2], position=row[3], is_verified=row[4]
                     )
                 txo = txs[row[0]].outputs[row[5]]
-            row_accounts = {k: v for k, v in (a.split('|') for a in row[8].split(','))}
+            row_accounts = dict(a.split('|') for a in row[8].split(','))
             account_match = set(row_accounts) & my_accounts
             if account_match:
                 txo.is_my_account = True
diff --git a/torba/torba/client/basetransaction.py b/torba/torba/client/basetransaction.py
index d6c7eb76b..724ee3f2a 100644
--- a/torba/torba/client/basetransaction.py
+++ b/torba/torba/client/basetransaction.py
@@ -507,18 +507,17 @@ class BaseTransaction:
 
                 if tx._outputs:
                     break
-                else:
-                    # this condition and the outer range(5) loop cover an edge case
-                    # whereby a single input is just enough to cover the fee and
-                    # has some change left over, but the change left over is less
-                    # than the cost_of_change: thus the input is completely
-                    # consumed and no output is added, which is an invalid tx.
-                    # to be able to spend this input we must increase the cost
-                    # of the TX and run through the balance algorithm a second time
-                    # adding an extra input and change output, making tx valid.
-                    # we do this 5 times in case the other UTXOs added are also
-                    # less than the fee, after 5 attempts we give up and go home
-                    cost += cost_of_change + 1
+                # this condition and the outer range(5) loop cover an edge case
+                # whereby a single input is just enough to cover the fee and
+                # has some change left over, but the change left over is less
+                # than the cost_of_change: thus the input is completely
+                # consumed and no output is added, which is an invalid tx.
+                # to be able to spend this input we must increase the cost
+                # of the TX and run through the balance algorithm a second time
+                # adding an extra input and change output, making tx valid.
+                # we do this 5 times in case the other UTXOs added are also
+                # less than the fee, after 5 attempts we give up and go home
+                cost += cost_of_change + 1
 
             if sign:
                 await tx.sign(funding_accounts)
diff --git a/torba/torba/coin/bitcoinsegwit.py b/torba/torba/coin/bitcoinsegwit.py
index 22b451147..b9856cf58 100644
--- a/torba/torba/coin/bitcoinsegwit.py
+++ b/torba/torba/coin/bitcoinsegwit.py
@@ -14,11 +14,11 @@ from torba.client.baseheader import BaseHeaders, ArithUint256
 
 
 class MainHeaders(BaseHeaders):
-    header_size = 80
-    chunk_size = 2016
-    max_target = 0x00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+    header_size: int = 80
+    chunk_size: int = 2016
+    max_target: int = 0x00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff
     genesis_hash: Optional[bytes] = b'000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f'
-    target_timespan = 14 * 24 * 60 * 60
+    target_timespan: int = 14 * 24 * 60 * 60
 
     @staticmethod
     def serialize(header: dict) -> bytes: