diff --git a/liteeth/test/arp_tb.py b/liteeth/test/arp_tb.py
index 373a48018..3cd9ad362 100644
--- a/liteeth/test/arp_tb.py
+++ b/liteeth/test/arp_tb.py
@@ -50,7 +50,7 @@ class TB(Module):
 		while selfp.arp.table.response.stb != 1:
 			selfp.arp.table.response.ack = 1
 			yield
-		print("Model's MAC : 0x%12x" %selfp.arp.table.response.mac_address)
+		print("Received MAC : 0x{:12x}".format(selfp.arp.table.response.mac_address))
 
 
 if __name__ == "__main__":
diff --git a/liteeth/test/ip_tb.py b/liteeth/test/ip_tb.py
index 96b6d3418..1c21ffa5c 100644
--- a/liteeth/test/ip_tb.py
+++ b/liteeth/test/ip_tb.py
@@ -51,7 +51,7 @@ class TB(Module):
 
 			selfp.ip_port.source.ack = 1
 			if selfp.ip_port.source.stb == 1 and selfp.ip_port.source.sop == 1:
-				print("IP Packet / from ip_address %08x" %selfp.ip_port.sink.ip_address)
+				print("packet from from IP 0x{:08x}".format(selfp.ip_port.sink.ip_address))
 
 			yield
 
diff --git a/liteeth/test/model/arp.py b/liteeth/test/model/arp.py
index 7a23f23ff..677904cc7 100644
--- a/liteeth/test/model/arp.py
+++ b/liteeth/test/model/arp.py
@@ -33,10 +33,10 @@ class ARPPacket(Packet):
 	def __repr__(self):
 		r = "--------\n"
 		for k in sorted(arp_header.keys()):
-			r += k + " : 0x%x" %getattr(self,k) + "\n"
+			r += k + " : 0x{:0x}\n".format(getattr(self,k))
 		r += "payload: "
 		for d in self:
-			r += "%02x" %d
+			r += "{:02x}".format(d)
 		return r
 
 class ARP(Module):
diff --git a/liteeth/test/model/icmp.py b/liteeth/test/model/icmp.py
index 8a27b61f9..cf54b17c3 100644
--- a/liteeth/test/model/icmp.py
+++ b/liteeth/test/model/icmp.py
@@ -31,10 +31,10 @@ class ICMPPacket(Packet):
 	def __repr__(self):
 		r = "--------\n"
 		for k in sorted(icmp_header.keys()):
-			r += k + " : 0x%x" %getattr(self,k) + "\n"
+			r += k + " : 0x{:0x}\n".format(getattr(self,k))
 		r += "payload: "
 		for d in self:
-			r += "%02x" %d
+			r += "{:02x}".format(d)
 		return r
 
 class ICMP(Module):
diff --git a/liteeth/test/model/ip.py b/liteeth/test/model/ip.py
index 964284470..03c5f8b58 100644
--- a/liteeth/test/model/ip.py
+++ b/liteeth/test/model/ip.py
@@ -55,10 +55,10 @@ class IPPacket(Packet):
 	def __repr__(self):
 		r = "--------\n"
 		for k in sorted(ipv4_header.keys()):
-			r += k + " : 0x%x" %getattr(self,k) + "\n"
+			r += k + " : 0x{:0x}\n".format(getattr(self,k))
 		r += "payload: "
 		for d in self:
-			r += "%02x" %d
+			r += "{:02x}".format(d)
 		return r
 
 class IP(Module):
@@ -101,7 +101,7 @@ class IP(Module):
 			received = packet.get_checksum()
 			packet.insert_checksum()
 			expected = packet.get_checksum()
-			raise ValueError("Checksum error received %04x / expected %04x" %(received, expected))
+			raise ValueError("Checksum error received {:04x} / expected {:04x}".format(received, expected))
 		packet.decode()
 		if self.debug:
 			print_ip("<<<<<<<<")
diff --git a/liteeth/test/model/mac.py b/liteeth/test/model/mac.py
index f18f49906..9267f88bb 100644
--- a/liteeth/test/model/mac.py
+++ b/liteeth/test/model/mac.py
@@ -77,10 +77,10 @@ class MACPacket(Packet):
 	def __repr__(self):
 		r = "--------\n"
 		for k in sorted(mac_header.keys()):
-			r += k + " : 0x%x" %getattr(self,k) + "\n"
+			r += k + " : 0x{:0x}\n".format(getattr(self,k))
 		r += "payload: "
 		for d in self:
-			r += "%02x" %d
+			r += "{:02x}".format(d)
 		return r
 
 class MAC(Module):
diff --git a/liteeth/test/model/phy.py b/liteeth/test/model/phy.py
index 8fc716295..1401110fe 100644
--- a/liteeth/test/model/phy.py
+++ b/liteeth/test/model/phy.py
@@ -35,7 +35,7 @@ class PHY(Module):
 			r = ">>>>>>>>\n"
 			r += "length " + str(len(datas)) + "\n"
 			for d in datas:
-				r += "%02x" %d
+				r += "{:02x}".format(d)
 			print_phy(r)
 		self.phy_source.send(packet)
 
@@ -45,7 +45,7 @@ class PHY(Module):
 			r = "<<<<<<<<\n"
 			r += "length " + str(len(self.phy_sink.packet)) + "\n"
 			for d in self.phy_sink.packet:
-				r += "%02x" %d
+				r += "{:02x}".format(d)
 			print_phy(r)
 		self.packet = self.phy_sink.packet
 
diff --git a/liteeth/test/model/udp.py b/liteeth/test/model/udp.py
index 7179b9ff2..1892a2d56 100644
--- a/liteeth/test/model/udp.py
+++ b/liteeth/test/model/udp.py
@@ -31,10 +31,10 @@ class UDPPacket(Packet):
 	def __repr__(self):
 		r = "--------\n"
 		for k in sorted(udp_header.keys()):
-			r += k + " : 0x%x" %getattr(self,k) + "\n"
+			r += k + " : 0x{:0x}\n".format(getattr(self,k))
 		r += "payload: "
 		for d in self:
-			r += "%02x" %d
+			r += "{:02x}".format(d)
 		return r
 
 class UDP(Module):