diff --git a/mmgen/altcoins/eth/tx.py b/mmgen/altcoins/eth/tx.py
index 51d61b78..b7456c95 100755
--- a/mmgen/altcoins/eth/tx.py
+++ b/mmgen/altcoins/eth/tx.py
@@ -89,7 +89,8 @@ class EthereumMMGenTX:
 			if getattr(opt,'contract_data',None):
 				m = "'--contract-data' option may not be used with token transaction"
 				assert not 'Token' in type(self).__name__, m
-				self.usr_contract_data = HexStr(open(opt.contract_data).read().strip())
+				with open(opt.contract_data) as fp:
+					self.usr_contract_data = HexStr(fp.read().strip())
 				self.disable_fee_check = True
 
 		async def get_nonce(self):
diff --git a/mmgen/cfg.py b/mmgen/cfg.py
index d24de8ac..0a9e844e 100755
--- a/mmgen/cfg.py
+++ b/mmgen/cfg.py
@@ -49,7 +49,8 @@ class CfgFile(object):
 	def __init__(self):
 		self.fn = os.path.join(self.fn_dir,self.fn_base)
 		try:
-			self.data = open(self.fn).read().splitlines()
+			with open(self.fn) as fp:
+				self.data = fp.read().splitlines()
 		except:
 			if self.warn_missing:
 				self.warn_missing_file( div=self.fn, fmt_args=(self.desc,self.fn) )
@@ -61,7 +62,8 @@ class CfgFile(object):
 		if src.data:
 			data = src.data + src.make_metadata() if self.write_metadata else src.data
 			try:
-				open(self.fn,'w').write('\n'.join(data)+'\n')
+				with open(self.fn,'w') as fp:
+					fp.write('\n'.join(data)+'\n')
 				os.chmod(self.fn,0o600)
 			except:
 				die(2,f'ERROR: unable to write to {self.fn!r}')
@@ -184,7 +186,8 @@ class CfgFileSampleSys(CfgFileSample):
 	def __init__(self):
 		if os.getenv('MMGEN_TEST_SUITE_CFGTEST'):
 			self.fn = os.path.join(g.data_dir_root,self.test_fn_subdir,self.fn_base)
-			self.data = open(self.fn).read().splitlines()
+			with open(self.fn) as fp:
+				self.data = fp.read().splitlines()
 		else:
 			# self.fn is used for error msgs only, so file need not exist on filesystem
 			self.fn = os.path.join(os.path.dirname(__file__),'data',self.fn_base)
diff --git a/mmgen/daemon.py b/mmgen/daemon.py
index fb38b526..63061183 100755
--- a/mmgen/daemon.py
+++ b/mmgen/daemon.py
@@ -107,7 +107,8 @@ class Daemon(Lockable):
 	@property
 	def pid(self):
 		if self.use_pidfile:
-			return open(self.pidfile).read().strip()
+			with open(self.pidfile) as fp:
+				return fp.read().strip()
 		elif self.platform == 'win':
 			"""
 			Assumes only one running instance of given daemon.  If multiple daemons are running,
@@ -471,7 +472,8 @@ class CoinDaemon(Daemon):
 
 		if self.test_suite or self.network == 'regtest':
 			if self.cfg_file and not self.flag.keep_cfg_file:
-				open(f'{self.datadir}/{self.cfg_file}','w').write(self.cfg_file_hdr)
+				with open(f'{self.datadir}/{self.cfg_file}','w') as fp:
+					fp.write(self.cfg_file_hdr)
 
 		if self.use_pidfile and os.path.exists(self.pidfile):
 			# Parity overwrites the data in the existing pidfile without zeroing it first, leading
diff --git a/mmgen/led.py b/mmgen/led.py
index 28de1a2f..482f9f53 100755
--- a/mmgen/led.py
+++ b/mmgen/led.py
@@ -98,8 +98,11 @@ class LEDControl:
 
 		def check_access(fn,desc,init_val=None):
 			try:
-				iv = init_val or open(fn).read().strip()
-				open(fn,'w').write(f'{iv}\n')
+				if not init_val:
+					with open(fn) as fp:
+						init_val = fp.read().strip()
+				with open(fn,'w') as fp:
+					fp.write(f'{init_val}\n')
 				return True
 			except PermissionError:
 				ydie(1,'\n'+fmt(f"""
@@ -119,8 +122,10 @@ class LEDControl:
 	@classmethod
 	def create_dummy_control_files(cls):
 		db = cls.boards['dummy']
-		open(db.status,'w').write('0\n')
-		open(db.trigger,'w').write(db.trigger_states[1]+'\n')
+		with open(db.status,'w') as fp:
+			fp.write('0\n')
+		with open(db.trigger,'w') as fp:
+			fp.write(db.trigger_states[1]+'\n')
 
 	def noop(self,*args,**kwargs): pass
 
@@ -134,7 +139,8 @@ class LEDControl:
 			msg(f'led_loop({on_secs},{off_secs})')
 
 		if not on_secs:
-			open(self.board.status,'w').write('0\n')
+			with open(self.board.status,'w') as fp:
+				fp.write('0\n')
 			while True:
 				if self.ev_sleep(3600):
 					return
@@ -143,7 +149,8 @@ class LEDControl:
 			for s_time,val in ((on_secs,255),(off_secs,0)):
 				if self.debug:
 					msg_r(('^','+')[bool(val)])
-				open(self.board.status,'w').write(f'{val}\n')
+				with open(self.board.status,'w') as fp:
+					fp.write(f'{val}\n')
 				if self.ev_sleep(s_time):
 					if self.debug:
 						msg('\n')
@@ -178,4 +185,5 @@ class LEDControl:
 			msg('Stopping LED')
 
 		if self.board.trigger:
-			open(self.board.trigger,'w').write(self.board.trigger_states[1]+'\n')
+			with open(self.board.trigger,'w') as fp:
+				fp.write(self.board.trigger_states[1]+'\n')
diff --git a/mmgen/main_autosign.py b/mmgen/main_autosign.py
index 38113cc9..58b7be0e 100755
--- a/mmgen/main_autosign.py
+++ b/mmgen/main_autosign.py
@@ -326,7 +326,8 @@ def create_key():
 	desc = f'key file {fn!r}'
 	msg('Creating ' + desc)
 	try:
-		open(fn,'w').write(kdata+'\n')
+		with open(fn,'w') as fp:
+			fp.write(kdata+'\n')
 		os.chmod(fn,0o400)
 		msg('Wrote ' + desc)
 	except:
diff --git a/mmgen/util.py b/mmgen/util.py
index 660822f1..a04bba49 100755
--- a/mmgen/util.py
+++ b/mmgen/util.py
@@ -638,7 +638,8 @@ def write_data_to_file( outfile,data,desc='data',
 		# if cmp_data is empty, file can be either empty or non-existent
 		if check_data:
 			try:
-				d = open(outfile,('r','rb')[bool(binary)]).read()
+				with open(outfile,('r','rb')[bool(binary)]) as fp:
+					d = fp.read()
 			except:
 				d = ''
 			finally:
diff --git a/scripts/exec_wrapper.py b/scripts/exec_wrapper.py
index fdab3fd7..01967cbc 100755
--- a/scripts/exec_wrapper.py
+++ b/scripts/exec_wrapper.py
@@ -47,7 +47,8 @@ def exec_wrapper_write_traceback():
 	c = exec_wrapper_get_colors()
 	sys.stdout.write('{}{}'.format(c.yellow(''.join(lines)),c.red(exc)))
 
-	open('my.err','w').write(''.join(lines+[exc]))
+	with open('my.err','w') as fp:
+		fp.write(''.join(lines+[exc]))
 
 def exec_wrapper_end_msg():
 	if os.getenv('EXEC_WRAPPER_SPAWN') and not os.getenv('MMGEN_TEST_SUITE_DETERMINISTIC'):
@@ -61,7 +62,9 @@ exec_wrapper_tstart = time.time()
 try:
 	sys.argv.pop(0)
 	exec_wrapper_execed_file = sys.argv[0]
-	exec(open(sys.argv[0]).read())
+	with open(sys.argv[0]) as fp:
+		text = fp.read()
+	exec(text)
 except SystemExit as e:
 	if e.code != 0 and not os.getenv('EXEC_WRAPPER_NO_TRACEBACK'):
 		exec_wrapper_write_traceback()
diff --git a/scripts/gendiff.py b/scripts/gendiff.py
index 5b395fa2..037f8d94 100755
--- a/scripts/gendiff.py
+++ b/scripts/gendiff.py
@@ -24,7 +24,8 @@ translate = {
 }
 
 def cleanup_file(fn):
-	data = open(fn).read()
+	with open(fn) as fp:
+		data = fp.read()
 	def gen_text():
 		for line in data.splitlines():
 			line = re.sub('\r\n','\n',line) # DOS CRLF to Unix LF
@@ -32,8 +33,10 @@ def cleanup_file(fn):
 			line = re.sub(r'\s+$','',line)  # trailing whitespace
 			yield line
 	ret = list(gen_text())
-	open(fn+'.orig','w').write(data)
-	open(fn,'w').write('\n'.join(ret))
+	with open(fn+'.orig','w') as fp:
+		fp.write(data)
+	with open(fn,'w') as fp:
+		fp.write('\n'.join(ret))
 	return ret
 
 cleaned_texts = [cleanup_file(fn) for fn in fns]
diff --git a/test/test_py_d/ts_autosign.py b/test/test_py_d/ts_autosign.py
index e855e8ef..876c786f 100755
--- a/test/test_py_d/ts_autosign.py
+++ b/test/test_py_d/ts_autosign.py
@@ -129,7 +129,8 @@ class TestSuiteAutosign(TestSuiteBase):
 			for n in (1,2):
 				bad_tx = joinpath(mountpoint,'tx',f'bad{n}.rawtx')
 				if include_bad_tx and not remove_signed_only:
-					open(bad_tx,'w').write('bad tx data')
+					with open(bad_tx,'w') as fp:
+						fp.write('bad tx data')
 				if not include_bad_tx:
 					try: os.unlink(bad_tx)
 					except: pass
diff --git a/test/test_py_d/ts_ethdev.py b/test/test_py_d/ts_ethdev.py
index f444ac35..76675166 100755
--- a/test/test_py_d/ts_ethdev.py
+++ b/test/test_py_d/ts_ethdev.py
@@ -392,7 +392,8 @@ class TestSuiteEthdev(TestSuiteBase,TestSuiteShared):
 			if cp.returncode:
 				die(1,cp.stderr.decode())
 			keyfile = os.path.join(keystore,os.listdir(keystore)[0])
-			return json.loads(open(keyfile).read())['address']
+			with open(keyfile) as fp:
+				return json.loads(fp.read())['address']
 
 		def make_genesis(signer_addr,prealloc_addr):
 			return {
diff --git a/test/test_py_d/ts_input.py b/test/test_py_d/ts_input.py
index c2357985..f71fbd1b 100755
--- a/test/test_py_d/ts_input.py
+++ b/test/test_py_d/ts_input.py
@@ -113,7 +113,8 @@ class TestSuiteInput(TestSuiteBase):
 		return t
 
 	def get_passphrase_cmdline(self):
-		open('test/trash/pwfile','w').write('reference password\n')
+		with open('test/trash/pwfile','w') as fp:
+			fp.write('reference password\n')
 		t = self.spawn('test/misc/get_passphrase.py', [
 			'--usr-randchars=0',
 			'--label=MyLabel',
diff --git a/test/unit_tests_d/ut_rpc.py b/test/unit_tests_d/ut_rpc.py
index c7b6122e..3768dc92 100755
--- a/test/unit_tests_d/ut_rpc.py
+++ b/test/unit_tests_d/ut_rpc.py
@@ -16,7 +16,8 @@ def cfg_file_auth_test(proto,d):
 	os.makedirs(d.network_datadir)
 
 	cf = os.path.join(d.datadir,d.cfg_file)
-	open(cf,'a').write('\nrpcuser = ut_rpc\nrpcpassword = ut_rpc_passw0rd\n')
+	with open(cf,'a') as fp:
+		fp.write('\nrpcuser = ut_rpc\nrpcpassword = ut_rpc_passw0rd\n')
 
 	d.flag.keep_cfg_file = True
 	d.start()
diff --git a/test/unit_tests_d/ut_tx.py b/test/unit_tests_d/ut_tx.py
index e2c3b8a9..411df5ce 100755
--- a/test/unit_tests_d/ut_tx.py
+++ b/test/unit_tests_d/ut_tx.py
@@ -53,7 +53,9 @@ class unit_tests:
 			# New in version 3.3: Support for the unicode legacy literal (u'value') was
 			# reintroduced to simplify the maintenance of dual Python 2.x and 3.x codebases.
 			# See PEP 414 for more information.
-			chk = re.subn(r"\bu(['\"])",r"\1",open(fpath).read())[0] # remove Python2 'u' string prefixes from ref files
+			with open(fpath) as fp:
+				# remove Python2 'u' string prefixes from ref files
+				chk = re.subn( r"\bu(['\"])", r'\1', fp.read() )[0]
 			diff = get_ndiff(chk,text)
 			#print('\n'.join(diff))
 			nLines = len([i for i in diff if i.startswith('-')])
diff --git a/test/unit_tests_d/ut_tx_deserialize.py b/test/unit_tests_d/ut_tx_deserialize.py
index 6495ac23..26fbed17 100755
--- a/test/unit_tests_d/ut_tx_deserialize.py
+++ b/test/unit_tests_d/ut_tx_deserialize.py
@@ -98,7 +98,8 @@ class unit_test(object):
 			self._get_core_repo_root()
 			fn_b = 'src/test/data/tx_valid.json'
 			fn = os.path.join(self.core_repo_root,fn_b)
-			data = json.loads(open(fn).read())
+			with open(fn) as fp:
+				data = json.loads(fp.read())
 			print_info(fn_b,'Core test vector')
 			n = 1
 			for e in data: