diff --git a/README.md b/README.md
index 3ef8531..0677a35 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@
 - references
 	- [icon-json-rpc-v3](./references/icon-json-rpc-v3.md)
 	- [java-sdk](./references/java-sdk.md)
+	- [python-api-reference](./references/python-api-reference.md)
 	- [swift-api-reference](./references/swift-api-reference.md)
 	- [swift-sdk](./references/swift-sdk.md)
 - score
diff --git a/references/python-api-reference.md b/references/python-api-reference.md
new file mode 100644
index 0000000..c0c6cfc
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+++ b/references/python-api-reference.md
@@ -0,0 +1,917 @@
+---
+
+title: "ICON Python SDK API Reference"
+excerpt: ""
+
+---
+
+## Querying API Methods
+
+### Examples
+
+```python
+from iconsdk.builder.call_builder import CallBuilder
+
+# Returns block information by block height
+block = icon_service.get_block(1000)    		 
+
+# Returns block information by block hash
+block = icon_service.get_block("0x000...000")
+
+# Returns the last block information
+block = icon_service.get_block("latest")    	
+
+# Returns the balance of the account of given address
+balance = icon_service.get_balance("hx000...1")
+
+# Returns a list of the SCORE APIs
+score_apis = icon_service.get_score_api("cx000...1")
+
+# Returns the total supply of ICX
+total_supply = icon_service.get_total_supply()
+
+# Returns information about a transaction requested by transaction hash
+tx = icon_service.get_transaction("0x000...000")
+
+# Returns the result of a transaction by transaction hash
+tx_result = icon_service.get_transaction_result("0x000...000")
+
+# Generates a call instance using the CallBuilder
+call = CallBuilder().from_(wallet.get_address())\
+                    .to("cx000...1")\
+                    .method("balance_of")\
+                    .params({"address": "hx000...1"})\
+                    .build()
+
+# Executes a call method to call a read-only API method on the SCORE immediately without creating a transaction on Loopchain
+result = icon_service.call(call)
+
+```
+
+
+
+### Error Cases
+
+There are different types of error cases as below.  The exception is raised with the specific message. You can get more information about the exception from the message.   
+
+- **KeyStoreException** 
+  - It is raised when making or loading a key store file.  
+  - Error code for the exception is 1. 
+
+- **AddressException**
+  - It is raised when the address is invalid. 
+  - Error code for the exception is 2. 
+
+- **BalanceException**
+  - It is raised when the balance is invalid.
+  - Error code for the exception is 3. 
+- **DataTypeException**
+  - It is raised when the data type is invalid.
+  - Error code for the exception is 4. 
+
+- **JSONRPCException**
+  - It is raised when JSON-RPC response is an error.  
+  - Error code for the exception is 5. 
+
+- **ZipException**
+  - It is raised while writing zip in memory.
+  - Error code for the exception is 6. 
+
+
+
+### get_block
+
+``````python
+get_block(value)
+``````
+
+* Function A
+  -  Returns block information by block height
+  -  Delegates to **icx_getBlockByHeight** RPC method
+
+* Function B
+  * Returns block information by block hash
+  * Delegates to **icx_getBlockByHash** RPC method
+
+* Function C
+  * Returns the last block information
+  * Delegates to **icx_getLastBlock** RPC method
+
+#### Parameters
+
+* Function A
+  * value : Integer of a block height
+* Function B
+  * value : Hash of a block prefixed with '0x'
+* Function C
+  * value : 'latest'
+
+#### Returns
+
+Block data
+
+[Example of a returned block data](https://github.com/icon-project/icon-rpc-server/blob/master/docs/icon-json-rpc-v3.md#icx_getlastblock)
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid. 
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Returns block information by block height
+block = icon_service.get_block(1000)    		 
+
+# Returns block information by block hash
+block = icon_service.get_block("0x000...000")
+
+# Returns the last block information
+block = icon_service.get_block("latest")  
+```
+
+
+
+### get_balance
+
+```python
+get_balance(address: str)
+```
+
+Returns the ICX balance of the given EOA or SCORE
+
+Delegates to **icx_getBalance** RPC method
+
+#### Parameters
+
+address : An address of EOA or SCORE
+
+#### Returns
+
+Number of ICX coins
+
+#### Error Cases
+
+* AddressException : Address is invalid. 
+* DataTypeException : Data type is invalid.
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Returns the ICX balance of the given EOA or SCORE
+balance = icon_service.get_balance("hx000...1")
+```
+
+
+
+### get_score_api
+
+```python
+get_score_api(address: str)
+```
+
+Returns SCORE's external API list
+
+Delegates to **icx_getScoreApi** RPC method
+
+#### Parameters
+
+address : A SCORE address to be examined
+
+#### Returns
+
+A list of API methods of the SCORE and its information
+
+Fields :
+
+* type : Method type;  function, fallback, or eventlog
+* name : Function name on the SCORE
+* inputs : A list of information of parameters
+  * name : Parameter name
+  * type : Parameter type ; int, str, bytes, bool, Address
+  * indexed : In the case of eventlog, tells if the parameter is indexed.
+* outputs : Return value
+  * type : Return value type ; int, str, bytes, bool, Address
+* Readonly : External (readonly=True)
+* Payable: Payable
+
+#### Error Cases
+
+* AddressException : Address is invalid.
+* DataTypeException : Data type is invalid.
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Returns SCORE's external API list
+score_apis = icon_service.get_score_api("cx000...1")
+```
+
+
+
+### get_total_supply
+
+```python
+get_total_supply()
+```
+
+Returns total ICX coin supply that has been issued
+
+Delegates to **icx_getTotalSupply** RPC method
+
+#### Parameters
+
+None
+
+#### Returns
+
+Total number of ICX coins issued
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid.
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Returns total ICX coin supply that has been issued
+total_supply = icon_service.get_total_supply()
+```
+
+
+
+### get_transaction
+
+```python
+get_transaction(tx_hash: str)
+```
+
+Returns the transaction information requested by transaction hash
+
+Delegates to **icx_getTransactionByHash** RPC method
+
+#### Parameters
+
+tx_hash : Transaction hash prefixed with '0x'
+
+#### Returns
+
+Information about a transaction
+
+Fields :
+
+- version : Protocol version (3 for V3)
+- from : An EOA address that created the transaction
+- to : An EOA address to receive coins, or SCORE address to execute the transaction
+- value : Amount of ICX coins in loop to transfer. When omitted, assumes 0. (1 icx = 10 ^ 18 loop)
+- stepLimit :  Maximum step allowance that can be used by the transaction
+- timestamp : Transaction creation time. Timestamp is in microseconds.
+- nid : Network ID (1 for Main net, etc)
+- nonce : An arbitrary number used to prevent transaction hash collision
+- txHash : Transaction hash
+- txIndex : Transaction index in a block. Null when it is pending.
+- blockHeight : Block height including the transaction. Null when it is pending
+- blockHash : Block hash including the transaction. Null when it is pending.
+- signature : Signature of the transaction
+- dataType : Data type; call, deploy, message
+- data : Contains various type of data depending on the dataType
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid.
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Returns the transaction information requested by transaction hash
+tx = icon_service.get_transaction("0x000...000")
+```
+
+
+
+### get_transaction_result
+
+```python
+get_transaction_result(tx_hash: str)
+```
+
+Returns the transaction result requested by transaction hash
+
+Delegates to **icx_getTransactionResult** RPC method
+
+#### Parameters
+
+tx_hash : Hash of a transaction prefixed with '0x'
+
+#### Returns
+
+A transaction result object
+
+Field :
+
+* status : 1 on success, 0 on failure
+* to : Recipient address of the transaction
+* failure : This field exists when status is 0. Contains code(str) and message(str)
+* txHash : Transaction hash
+* txIndex : Transaction index in the block
+* blockHeight : Block height including the transaction
+* blockHash : Block hash including the transaction
+* cumulativeStepUsed : Sum of stepUsed by this transaction and all preceding transactions in the same block
+* stepUsed : The amount of step used by this transaction
+* stepPrice: The step price used by this transaction
+* scoreAddress : A SCORE address if the transaction created a new SCORE. (optional)
+* eventLogs : Array of eventlogs generated by this transaction 
+* logsBloom : Bloom filter to quickly retrieve related eventlogs
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid.
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Returns the transaction result requested by transaction hash
+tx_result = icon_service.get_transaction_result("0x000...000")
+```
+
+
+
+### call
+
+```python
+call(call: Call)
+```
+
+Calls SCORE's external function which is read-only without creating a transaction on Loopchain
+
+Delegates to **icx_call** RPC method
+
+#### Parameters
+
+Call object made by **CallBuilder**
+
+Fields :
+
+* from : Message sender's address
+* to : A SCORE address that will handle the message
+* method : name of an external function
+* params : Parameters to be passed to the function (optional). A data type of params should be **dict**.
+
+
+#### Returns
+
+Values returned by the executed SCORE function
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid.
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Generates a call instance using the CallBuilder
+call = CallBuilder().from_(wallet.get_address())\
+                    .to("cx000...1")\
+                    .method("balance_of")\
+                    .params({"address": "hx000...1"})\
+                    .build()
+
+# Calls SCORE's external function which is read-only without creating a transaction on Loopchain
+result = icon_service.call(call)
+```
+
+
+
+## Loading a Wallet and Storing the Keystore
+
+To send transactions, first, you should make an instance of your wallet.  
+
+You can make an instance of the wallet using bytes of the private key or from a keystore file.
+
+### Examples
+
+```python
+from iconsdk.wallet.wallet import KeyWallet
+
+# Generates a wallet
+wallet = KeyWallet.create()
+
+# Loads a wallet from bytes of the private key
+wallet = KeyWallet.load(b'-B\x99...xedy')
+
+# Loads a wallet from a keystore file
+wallet = KeyWallet.load("./keystore", "password")
+
+# Stores a keystore file on the file path
+wallet.store("./keystore", "password") # throw exception if having an error.
+
+# Returns an Address
+wallet.get_address()
+
+# Returns a private key
+wallet.get_private_key()
+
+# Signs the transaction
+signature = wallet.sign(b'D8\xe9...\xfc')
+```
+
+
+
+## API Methods of KeyWallet
+
+### create
+
+```python
+create()
+```
+
+Generates an instance of Wallet without a specific private key
+
+#### Parameters
+
+None
+
+#### Returns
+
+An instance of Wallet class
+
+#### Example
+
+``````python
+# Generates a wallet
+wallet = KeyWallet.create()
+``````
+
+
+
+### load
+
+```python
+load(private_key: bytes)
+```
+
+Loads a wallet from bytes of the private key and generates an instance of Wallet
+
+#### Parameters
+
+private_key : Bytes of the private key
+
+#### Returns
+
+An instance of Wallet class
+
+#### Error Cases
+
+* DataTypeException : Private key is invalid.
+
+#### Example
+
+```python
+# Loads a wallet from bytes of the private key
+wallet = KeyWallet.load(b'-B\x99...xedy')
+```
+
+
+
+### load
+
+```python
+load(file_path, password)
+```
+
+Loads a wallet from a keystore file with your password and generates an instance of Wallet
+
+#### Parameters
+
+* file_path : File path of the keystore file
+
+* password : Password for the keystore file. Password must include alphabet character, number, and special character
+
+#### Returns
+
+An instance of Wallet class
+
+#### Error Cases
+
+* KeyStoreException: Key store file is invalid.
+
+#### Example
+
+```python
+# Loads a wallet from a keystore file
+wallet = KeyWallet.load("./keystore", "password")
+```
+
+
+
+### store
+
+```python
+store(file_path, password)
+```
+
+Stores data of an instance of a derived wallet class on the file path with your password
+
+#### Parameters
+
+- file_path : File path of the keystore file
+
+- password :  Password for the keystore file. Password must include alphabet character, number, and special character
+
+#### Returns
+
+None
+
+#### Error Cases
+
+* KeyStoreException: Key store file is invalid.
+
+#### Example
+
+```python
+# Stores a keystore file on the file path
+wallet.store("./keystore", "password") # throw exception if having an error.
+```
+
+
+
+### get_address
+
+```python
+get_address()
+```
+
+Returns an EOA address
+
+The format of your account (which is generated from your public key) is hxfd7e4560ba363f5aabd32caac7317feeee70ea57.
+
+#### Parameters
+
+None
+
+#### Returns
+
+ An EOA address
+
+#### Example
+
+```python
+# Returns an EOA address
+wallet.get_address()
+```
+
+
+
+### get_private_key
+
+```python
+get_private_key()
+```
+
+Returns hex string of the private key of the wallet
+
+#### Parameters
+
+None
+
+#### Returns
+
+Hex string of the private key 
+
+#### Example
+
+```python
+# Returns the private key
+wallet.get_private_key()
+```
+
+
+
+### sign
+
+```python
+sign(data: bytes)
+```
+
+Returns bytes of the ECDSA-SHA256 signature made from the data
+
+#### Parameters
+
+data : bytes of the transaction
+
+#### Returns
+
+Bytes of the signature
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid.
+
+#### Example
+
+``` python
+# Signs the transaction
+signature = wallet.sign(b'D8\xe9...\xfc')
+```
+
+
+
+## Signing and Sending Transaction
+
+### Generating a Transaction
+
+After then, you should create an instance of the transaction using different types of **transaction builders** as follows.  
+
+### Signing a Transaction
+
+Before sending a transaction, the transaction should be signed by using **SignedTransaction** class. The SignedTransaction class is used to sign the transaction by returning an instance of the signed transaction as demonstrated in the example below. The instance of the signed transaction has the property of a signature.  
+
+### Sending a Transaction
+
+Finally, you can send a transaction with the signed transaction object as follows.
+
+### Examples
+
+```python
+from iconsdk.builder.transaction_builder import (
+    TransactionBuilder,
+    DeployTransactionBuilder,
+    CallTransactionBuilder,
+    MessageTransactionBuilder
+)
+from iconsdk.signed_transaction import SignedTransaction
+
+# Generates an instance of transaction for sending icx.
+transaction = TransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .value(150000000)\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .build()
+
+# Generates an instance of transaction for deploying SCORE.
+transaction = DeployTransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .content_type("application/zip")\
+    .content(b'D8\xe9...\xfc')\
+    .params(params)\
+    .build()
+
+# Generates an instance of transaction for calling method in SCORE.
+transaction = CallTransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .method("transfer")\
+    .params(params)\
+    .build()
+
+# Generates an instance of transaction for sending a message.
+transaction = MessageTransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .data("test")\
+    .build()
+
+# Returns the signed transaction object having a signature
+signed_transaction = SignedTransaction(transaction, wallet)
+
+# Sends the transaction
+tx_hash = icon_service.send_transaction(signed_transaction)
+```
+
+
+
+### TransactionBuilder
+
+Builder for a **Transaction** object
+
+#### Methods
+
+* from_ : The wallet address making a transaction. The default address is your account address.
+* to : The wallet address to receive coin or SCORE address to receive a transaction.
+* value : The amount of ICX to be sent. (Optional)
+* step_limit : The maximum step value for processing a transaction.
+* nid : Network ID. Default nid is 1 if you didn't set the value. (1 for Main net, etc)
+* nonce :  An arbitrary number used to prevent transaction hash collision. (Optional)
+* version : Protocol version (3 for V3). The default version is 3 if you didn't set the value.
+* timestamp : Transaction creation time. Timestamp is in microseconds. Default timestamp is set, if you didn't set the value.
+* build : Returns an ICX transaction object
+
+#### Returns
+
+A transaction object  
+
+#### Example
+
+```python
+# Generates an instance of transaction for sending icx.
+transaction = TransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .value(150000000)\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .build()
+```
+
+
+
+### DeployTransactionBuilder
+
+Builder for **DeployTransaction** object
+
+#### Methods
+
+* from_ : The wallet address making a transaction. The default address is your account address.
+* to : The wallet address to receive coin or SCORE address to receive a transaction
+* step_limit : The maximum step value for processing a transaction
+* nid : Network ID. Default nid is 1 if you didn't set the value. (1 for Main net, etc)
+* nonce : An arbitrary number used to prevent transaction hash collision
+* content_type : Content's MIME type
+* content : Binary data of the SCORE
+* params : Parameters passed on the SCORE methods ; on_install (), on_update (). Data type of the params should be **dict**. (optional)
+* version : Protocol version (3 for V3). The default version is 3 if you didn't set the value.
+* timestamp : Transaction creation time. Timestamp is in microseconds. Default timestamp is set, if you didn't set the value.
+* build : Returns a deploy transaction object
+
+#### Returns
+
+A deploy transaction object  
+
+#### Example
+
+```python
+# Generates an instance of transaction for deploying SCORE.
+transaction = DeployTransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .content_type("application/zip")\
+    .content(b'D8\xe9...\xfc')\
+    .params(params)\
+    .build()
+```
+
+
+
+### CallTransactionBuilder
+
+Builder for **CallTransaction** object
+
+#### Methods
+
+- from_ : The wallet address making a transaction. The default address is your account address.
+- to : The wallet address to receive coin or SCORE address to receive a transaction
+- step_limit : The maximum step value for processing a transaction
+- nid : Network ID. Default nid is 1 if you didn't set the value. (1 for Main net, etc)
+- nonce :  An arbitrary number used to prevent transaction hash collision
+- method : Methods in the SCORE
+- params : Parameters passed on the SCORE methods. Data type of the params should be **dict**. (optional) 
+- version : Protocol version (3 for V3). The default version is 3 if you didn't set the value.
+- timestamp : Transaction creation time. Timestamp is in microseconds. Default timestamp is set, if you didn't set the value.
+- Build : Returns a call transaction object  
+
+#### Returns
+
+A call transaction object  
+
+#### Example
+
+```python
+# Generates an instance of transaction for calling method in SCORE.
+transaction = CallTransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .method("transfer")\
+    .params(params)\
+    .build()
+```
+
+
+
+### MessageTransactionBuilder
+
+Builder for **MessageTransaction** object
+
+#### Methods
+
+- from_ : The wallet address making a transaction. The default address is your account address.
+- to : The wallet address to receive coin or SCORE address to receive a transaction
+- stepLimit : The maximum step value for processing a transaction
+- nid : Network ID. Default nid is 1 if you didn't set the value. (1 for Main net, etc)
+- nonce :  An arbitrary number used to prevent transaction hash collision
+- data : Data by the dataType. Data type of the data should be **string**.
+- version : Protocol version (3 for V3). The default version is 3 if you didn't set the value.
+- timestamp : Transaction creation time. Timestamp is in microseconds. Default timestamp is set, if you didn't set the value.
+- build : Returns a message transaction object  
+
+#### Returns
+
+A message transaction object  
+
+#### Example
+
+```python
+# Generates an instance of transaction for sending a message.
+transaction = MessageTransactionBuilder()\
+    .from_(wallet.get_address())\
+    .to("cx00...02")\
+    .step_limit(1000000)\
+    .nid(3)\
+    .nonce(100)\
+    .data("test")\
+    .build()
+```
+
+
+
+### SignedTransaction
+
+```python
+SignedTransaction(transaction: Transaction, wallet: Wallet)
+```
+
+Returns the signed transaction object having a signature
+
+#### Parameters
+
+* transaction : A transaction object not having a signature field yet
+* wallet : A wallet object
+
+#### Returns
+
+The signed transaction object having a signature field finally
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid.
+
+#### Example
+
+```python
+# Returns the signed transaction object having a signature
+signed_transaction = SignedTransaction(transaction, wallet)
+```
+
+
+
+### send_transaction
+
+```python
+send_transaction(signed_transaction: SignedTransaction)
+```
+
+Sends the transaction
+
+Delegates to **icx_sendTransaction** RPC method
+
+Need to wait for a while after sending the transaction. Because it takes time to make a consensus among nodes. We recommend 0.3 second at least.
+
+#### Parameters
+
+signed_transaction : A signed transaction object
+
+#### Returns
+
+Transaction hash prefixed with '0x'
+
+#### Error Cases
+
+* DataTypeException : Data type is invalid.
+* JSONRPCException :  JSON-RPC Response is error.
+
+#### Example
+
+```python
+# Sends the transaction
+tx_hash = icon_service.send_transaction(signed_transaction)
+```
+
+### Reference
+- [ICON JSON-RPC API v3](icon-json-rpc-v3)
+- [ICON SDK for Python (Previous version)](https://github.com/icon-project/icon_sdk_for_python) - Reference to [ICON JSON-RPC API **v2**](https://github.com/icon-project/icx_JSON_RPC)
+