use startswith() instead of string indexing where feasible

mmgen/cfg.py

@@ -376,7 +376,7 @@ class Config(Lockable):
 
 	if os.getenv('MMGEN_DEBUG_ALL'):
 		for name in _env_opts:
-			if name[:11] == 'MMGEN_DEBUG':
+			if name.startswith('MMGEN_DEBUG'):
 				os.environ[name] = '1'
 
 	@property

mmgen/devtools.py

@@ -66,7 +66,7 @@ def get_stack_trace(message=None, nl='\n', sep='\n  ', trim=3):
 
 	import os, re, traceback
 
-	tb = [t for t in traceback.extract_stack() if t.filename[:1] != '<']
+	tb = [t for t in traceback.extract_stack() if not t.filename.startswith('<')]
 	fs = '{}:{}: in {}:\n    {}'
 	out = [
 		fs.format(

mmgen/fileutil.py

@@ -197,7 +197,7 @@ def write_data_to_file(
 				of = None # Windows
 
 			if of:
-				if of[:5] == 'pipe:':
+				if of.startswith('pipe:'):
 					if no_tty:
 						die(2, f'Writing {desc} to pipe is not allowed')
 					if ask_tty and not cfg.quiet:

mmgen/proto/eth/contract.py

@@ -150,7 +150,7 @@ class Token(Contract):
 	async def get_decimals(self):
 		ret = await self.do_call('decimals()')
 		try:
-			assert ret[:2] == '0x'
+			assert ret.startswith('0x')
 			return int(ret, 16)
 		except:
 			msg(f'RPC call to decimals() failed (returned {ret!r})')

mmgen/proto/eth/tx/base.py

@@ -139,7 +139,7 @@ class TokenBase(Base):
 			if self.is_swap:
 				d = rlp.decode(bytes.fromhex(self.serialized2))
 				data = d[5].hex()
-				assert data[:8] == '44bc937b', (
+				assert data.startswith('44bc937b'), (
 					f'{data[:8]}: invalid MethodID in router TX serialized data')
 				assert data[32:72] == self.token_vault_addr, (
 					f'{data[32:72]}: invalid vault address in router TX serialized data')

mmgen/tool/coin.py

@@ -157,7 +157,7 @@ class tool_cmd(tool_cmd_base):
 	def redeem_script2addr(self, redeem_script_hex: 'sstr'): # new
 		"convert a Segwit P2SH-P2WPKH redeem script to an address"
 		assert self.mmtype.name == 'segwit', 'This command is meaningful only for --type=segwit'
-		assert redeem_script_hex[:4] == '0014', f'{redeem_script_hex!r}: invalid redeem script'
+		assert redeem_script_hex.startswith('0014'), f'{redeem_script_hex!r}: invalid redeem script'
 		assert len(redeem_script_hex) == 44, f'{len(redeem_script_hex)//2} bytes: invalid redeem script length'
 		from ..proto.btc.common import hash160
 		return self.proto.pubhash2addr(hash160(bytes.fromhex(redeem_script_hex)), 'p2sh')

test/cmdtest_d/wallet.py

@@ -193,7 +193,7 @@ class CmdTestWalletConv(CmdTestBase, CmdTestShared):
 			t.expect('Enter brainwallet: ', ref_wallet_brainpass+'\n')
 		if icls.enc and icls.type != 'brain':
 			t.passphrase(icls.desc, self.wpasswd)
-			if self.test_name[:19] == 'ref_hincog_conv_old':
+			if self.test_name.startswith('ref_hincog_conv_old'):
 				t.expect('Is the Seed ID correct? (Y/n): ', '\n')
 			else:
 				t.expect(['Passphrase is OK', ' are correct'])