diff --git a/.gitignore b/.gitignore
index 0af19e5..210a6c8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@
 # Temporary data
 .ipynb_checkpoints/
 /examples/stats/.ipynb_checkpoints
+/.cache/
diff --git a/etherscan/__pycache__/__init__.cpython-36.pyc b/etherscan/__pycache__/__init__.cpython-36.pyc
new file mode 100644
index 0000000..669c23a
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diff --git a/etherscan/__pycache__/accounts.cpython-36.pyc b/etherscan/__pycache__/accounts.cpython-36.pyc
new file mode 100644
index 0000000..09172e5
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diff --git a/etherscan/__pycache__/client.cpython-36.pyc b/etherscan/__pycache__/client.cpython-36.pyc
new file mode 100644
index 0000000..57ec057
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diff --git a/etherscan/__pycache__/contracts.cpython-36.pyc b/etherscan/__pycache__/contracts.cpython-36.pyc
new file mode 100644
index 0000000..7e36b42
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diff --git a/etherscan/__pycache__/stats.cpython-36.pyc b/etherscan/__pycache__/stats.cpython-36.pyc
new file mode 100644
index 0000000..836fd7b
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diff --git a/etherscan/__pycache__/tokens.cpython-36.pyc b/etherscan/__pycache__/tokens.cpython-36.pyc
new file mode 100644
index 0000000..546cd08
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diff --git a/etherscan/accounts.py b/etherscan/accounts.py
index 72231f8..78eb8e0 100644
--- a/etherscan/accounts.py
+++ b/etherscan/accounts.py
@@ -5,45 +5,19 @@
 class Account(Client):
     def __init__(self, address=Client.dao_address, api_key='YourApiKeyToken'):
         Client.__init__(self, address=address, api_key=api_key)
-        self.module = self.URL_BASES['module'] + 'account'
-
-    def make_url(self, call_type=''):
-        if call_type == 'balance':
-            self.url = self.URL_BASES['prefix'] \
-                + self.module \
-                + self.action \
-                + self.address \
-                + self.tag \
-                + self.key
-        elif call_type == 'transactions':
-            self.url = self.URL_BASES['prefix'] \
-                + self.module \
-                + self.action \
-                + self.address \
-                + self.offset \
-                + self.page \
-                + self.key
-        elif call_type == 'blocks':
-            self.url = self.URL_BASES['prefix'] \
-                + self.module \
-                + self.action \
-                + self.address \
-                + self.blocktype \
-                + self.offset \
-                + self.page \
-                + self.key
+        self.url_dict[self.MODULE] = 'account'
 
     def get_balance(self):
-        self.action = self.URL_BASES['action'] + 'balance'
-        self.tag = self.URL_BASES['tag'] + 'latest'
-        self.make_url(call_type='transactions')
+        self.url_dict[self.ACTION] = 'balance'
+        self.url_dict[self.TAG] = 'latest'
+        self.build_url()
         req = self.connect()
         return req['result']
 
     def get_balance_multiple(self):
-        self.action = self.URL_BASES['action'] + 'balancemulti'
-        self.tag = self.URL_BASES['tag'] + 'latest'
-        self.make_url(call_type='balance')
+        self.url_dict[self.ACTION] = 'balancemulti'
+        self.url_dict[self.TAG] = 'latest'
+        self.build_url()
         req = self.connect()
         return req['result']
 
@@ -78,29 +52,29 @@ def get_transaction_page(self, page=1, offset=10000, sort='asc', internal=False)
             False -> (default) get normal external transactions
         """
         if internal:
-            self.action = self.URL_BASES['action'] + 'txlistinternal'
+            self.url_dict[self.ACTION] = 'txlistinternal'
         else:
-            self.action = self.URL_BASES['action'] + 'txlist'
-        self.page = self.URL_BASES['page'] + str(page)
-        self.offset = self.URL_BASES['offset'] + str(offset)
-        self.sort = self.URL_BASES['sort'] + sort
-        self.make_url(call_type='transactions')
+            self.url_dict[self.ACTION] = 'txlist'
+        self.url_dict[self.PAGE] = str(page)
+        self.url_dict[self.OFFSET] = str(offset)
+        self.url_dict[self.SORT] = sort
+        self.build_url()
         req = self.connect()
         return req['result']
 
     def get_all_transactions(self, offset=10000, sort='asc', internal=False) -> list:
         if internal:
-            self.action = self.URL_BASES['action'] + 'txlistinternal'
+            self.url_dict[self.ACTION] = 'txlistinternal'
         else:
-            self.action = self.URL_BASES['action'] + 'txlist'
-        self.page = self.URL_BASES['page'] + str(1)
-        self.offset = self.URL_BASES['offset'] + str(offset)
-        self.sort = self.URL_BASES['sort'] + sort
-        self.make_url(call_type='transactions')
+            self.url_dict[self.ACTION] = 'txlist'
+        self.url_dict[self.PAGE] = str(1)
+        self.url_dict[self.OFFSET] = str(offset)
+        self.url_dict[self.SORT] = sort
+        self.build_url()
 
         trans_list = []
         while True:
-            self.make_url(call_type='transactions')
+            self.build_url()
             req = self.connect()
             if "No transactions found" in req['message']:
                 print("Total number of transactions: {}".format(len(trans_list)))
@@ -109,9 +83,9 @@ def get_all_transactions(self, offset=10000, sort='asc', internal=False) -> list
             else:
                 trans_list += req['result']
                 # Find any character block that is a integer of any length
-                page_number = re.findall(r'[1-9](?:\d{0,2})(?:,\d{3})*(?:\.\d*[1-9])?|0?\.\d*[1-9]|0', self.page)
+                page_number = re.findall(r'[1-9](?:\d{0,2})(?:,\d{3})*(?:\.\d*[1-9])?|0?\.\d*[1-9]|0', self.url_dict[self.PAGE])
                 print("page {} added".format(page_number[0]))
-                self.page = self.URL_BASES['page'] + str(int(page_number[0]) + 1)
+                self.url_dict[self.PAGE] = str(int(page_number[0]) + 1)
 
     def get_blocks_mined_page(self, blocktype='blocks', page=1, offset=10000) -> list:
         """
@@ -124,22 +98,22 @@ def get_blocks_mined_page(self, blocktype='blocks', page=1, offset=10000) -> lis
             'blocks' -> full blocks only
             'uncles' -> uncles only
         """
-        self.action = self.URL_BASES['action'] + 'getminedblocks'
-        self.blocktype = self.URL_BASES['blocktype'] + blocktype
-        self.page = self.URL_BASES['page'] + str(page)
-        self.offset = self.URL_BASES['offset'] + str(offset)
-        self.make_url(call_type='blocks')
+        self.url_dict[self.ACTION] = 'getminedblocks'
+        self.url_dict[self.BLOCK_TYPE] = blocktype
+        self.url_dict[self.PAGE] = str(page)
+        self.url_dict[self.OFFSET] = str(offset)
+        self.build_url()
         req = self.connect()
         return req['result']
 
     def get_all_blocks_mined(self, blocktype='blocks', offset=10000) -> list:
-        self.action = self.URL_BASES['action'] + 'getminedblocks'
-        self.blocktype = self.URL_BASES['blocktype'] + blocktype
-        self.page = self.URL_BASES['page'] + str(1)
-        self.offset = self.URL_BASES['offset'] + str(offset)
+        self.url_dict[self.ACTION] = 'getminedblocks'
+        self.url_dict[self.BLOCK_TYPE] = blocktype
+        self.url_dict[self.PAGE] = str(1)
+        self.url_dict[self.OFFSET] = str(offset)
         blocks_list = []
         while True:
-            self.make_url(call_type='blocks')
+            self.build_url()
             req = self.connect()
             print(req['message'])
             if "No transactions found" in req['message']:
@@ -148,9 +122,9 @@ def get_all_blocks_mined(self, blocktype='blocks', offset=10000) -> list:
             else:
                 blocks_list += req['result']
                 # Find any character block that is a integer of any length
-                page_number = re.findall(r'[1-9](?:\d{0,2})(?:,\d{3})*(?:\.\d*[1-9])?|0?\.\d*[1-9]|0', self.page)
+                page_number = re.findall(r'[1-9](?:\d{0,2})(?:,\d{3})*(?:\.\d*[1-9])?|0?\.\d*[1-9]|0', self.url_dict[self.PAGE])
                 print("page {} added".format(page_number[0]))
-                self.page = self.URL_BASES['page'] + str(int(page_number[0]) + 1)
+                self.url_dict[self.PAGE] = str(int(page_number[0]) + 1)
 
     def get_internal_by_hash(self, tx_hash=''):
         """
diff --git a/etherscan/client.py b/etherscan/client.py
index 6bf8872..e52e560 100644
--- a/etherscan/client.py
+++ b/etherscan/client.py
@@ -1,44 +1,81 @@
 import requests
 import json
-
+import collections
 
 #  Assume user puts his API key in the api_key.json file under variable name "key"
 class Client(object):
     dao_address = '0xbb9bc244d798123fde783fcc1c72d3bb8c189413'
-    URL_BASES = dict(
-        prefix='https://api.etherscan.io/',
-        module='api?module=',
-        action='&action=',
-        tag='&tag=',
-        offset='&offset=',
-        page='&page=',
-        sort='&sort=',
-        blocktype='&blocktype=',
-        key='&apikey=',
-        address='&address=',
-    )
 
-    def __init__(self, address, api_key='YourApiKeyToken'):
+    # Constants
+    PREFIX = 'https://api.etherscan.io/api?'
+    MODULE = 'module='
+    ACTION = '&action='
+    TOKEN_NAME = '&tokenname='
+    CONTRACT_ADDRESS = '&contractaddress='
+    ADDRESS = '&address='
+    OFFSET = '&offset='
+    PAGE = '&page='
+    SORT = '&sort='
+    BLOCK_TYPE = '&blocktype='
+    TO = '&to='
+    VALUE = '&value='
+    DATA = '&data='
+    POSITION = '&='
+    HEX = '&hex='
+    GAS_PRICE = '&gasPrice='
+    GAS = '&gas='
+    START_BLOCK = '&startblock='
+    END_BLOCK = '&endblock='
+    BLOCKNO = '&blockno='
+    TXHASH = '&txhash='
+    TAG = '&tag='
+    BOOLEAN = '&boolean='
+    INDEX = '&index='
+    API_KEY = '&apikey='
+
+    url_dict = {}
+
+    def __init__(self, address, api_key=''):
         self.http = requests.session()
-        self.url = ''
-        self.module = ''
-        self.action = ''
-        self.tag = ''
-        self.offset = ''
-        self.page = ''
-        self.sort = ''
-        self.blocktype = ''
+        self.url_dict = collections.OrderedDict(
+            {
+                self.MODULE: '',
+                self.ADDRESS: '',
+                self.OFFSET: '',
+                self.PAGE: '',
+                self.SORT: '',
+                self.BLOCK_TYPE: '',
+                self.TO: '',
+                self.VALUE: '',
+                self.DATA: '',
+                self.POSITION: '',
+                self.HEX: '',
+                self.GAS_PRICE: '',
+                self.GAS: '',
+                self.START_BLOCK: '',
+                self.END_BLOCK: '',
+                self.BLOCKNO: '',
+                self.TXHASH: '',
+                self.TAG: '',
+                self.BOOLEAN: '',
+                self.INDEX: '',
+                self.API_KEY: api_key,
+            })
 
-        self.API_KEY = str(api_key)
+        # self.url_dict[API_KEY] = str(api_key)
         self.check_and_get_api()
-        self.key = self.URL_BASES['key'] + self.API_KEY
+        # self.key = self.URL_BASES['key'] + self.API_KEY
+
         if (len(address) > 20) and (type(address) == list):
             print("Etherscan only takes 20 addresses at a time")
             quit()
         elif (type(address) == list) and (len(address) <= 20):
-            self.address = self.URL_BASES['address'] + ','.join(address)
+            self.url_dict[self.ADDRESS] = ','.join(address)
         else:
-            self.address = self.URL_BASES['address'] + address
+            self.url_dict[self.ADDRESS] = address
+
+    def build_url(self):
+        self.url = self.PREFIX + ''.join([param + val if val else '' for param, val in self.url_dict.items()])
 
     def connect(self):
         # TODO: deal with "unknown exception" error
@@ -54,11 +91,11 @@ def connect(self):
                 print("Invalid Request")
                 exit()
         else:
-            print("problem with connection, status code: ", req.status_code)
+            print("Problem with connection, status code: ", req.status_code)
             exit()
 
     def check_and_get_api(self):
-        if self.API_KEY != 'YourApiKeyToken':
+        if self.url_dict[self.API_KEY]:  # Check if api_key is empty string
             pass
         else:
-            self.API_KEY = input('Please type your EtherScan.io API key: ')
+            self.url_dict[self.API_KEY] = input('Please type your EtherScan.io API key: ')
diff --git a/etherscan/contracts.py b/etherscan/contracts.py
index be21fb4..28c27a2 100644
--- a/etherscan/contracts.py
+++ b/etherscan/contracts.py
@@ -4,18 +4,10 @@
 class Contract(Client):
     def __init__(self, address=Client.dao_address, api_key='YourApiKeyToken'):
         Client.__init__(self, address=address, api_key=api_key)
-        self.module = self.URL_BASES['module'] + 'contract'
-
-    def make_url(self, call_type=''):
-        if call_type == 'getabi':
-            self.url = self.URL_BASES['prefix'] \
-                + self.module \
-                + self.action \
-                + self.address \
-                + self.key
+        self.url_dict[self.MODULE] = 'contract'
 
     def get_abi(self):
-        self.action = self.URL_BASES['action'] + 'getabi'
-        self.make_url(call_type='getabi')
+        self.url_dict[self.ACTION] = 'getabi'
+        self.build_url()
         req = self.connect()
-        return req['result']
\ No newline at end of file
+        return req['result']
diff --git a/etherscan/stats.py b/etherscan/stats.py
index 6fe74f2..1d61ecb 100644
--- a/etherscan/stats.py
+++ b/etherscan/stats.py
@@ -4,23 +4,16 @@
 class Stats(Client):
     def __init__(self, api_key='YourApiKeyToken'):
         Client.__init__(self, address='', api_key=api_key)
-        self.module = self.URL_BASES['module'] + 'stats'
-
-    def make_url(self, call_type=''):
-        if call_type == 'stats':
-            self.url = self.URL_BASES['prefix'] \
-                + self.module \
-                + self.action \
-                + self.key
+        self.url_dict[self.MODULE] = 'stats'
 
     def get_total_ether_supply(self):
-        self.action = self.URL_BASES['action'] + 'ethsupply'
-        self.make_url(call_type='stats')
+        self.url_dict[self.ACTION] = 'ethsupply'
+        self.build_url()
         req = self.connect()
         return req['result']
 
     def get_ether_last_price(self):
-        self.action = self.URL_BASES['action'] + 'ethprice'
-        self.make_url(call_type='stats')
+        self.url_dict[self.ACTION] = 'ethprice'
+        self.build_url()
         req = self.connect()
         return req['result']
diff --git a/etherscan/tokens.py b/etherscan/tokens.py
index 195b788..43087d8 100644
--- a/etherscan/tokens.py
+++ b/etherscan/tokens.py
@@ -4,34 +4,19 @@
 class Tokens(Client):
     def __init__(self, tokenname='TheDAO', api_key='YourApiKeyToken'):
         Client.__init__(self, address='', api_key=api_key)
-        self.tokenname = '&tokenname=' + tokenname
-
-    def make_url(self, call_type=''):
-        if call_type == 'tokensupply':
-            self.url = self.URL_BASES['prefix'] \
-                + self.module \
-                + self.action \
-                + self.tokenname \
-                + self.key
-        elif call_type == 'tokenbalance':
-            self.url = self.URL_BASES['prefix'] \
-                + self.module \
-                + self.action \
-                + self.tokenname \
-                + self.address \
-                + self.key
+        self.url_dict[self.TOKEN_NAME] = tokenname
 
     def get_total_supply(self):
-        self.action = self.URL_BASES['action'] + 'tokensupply'
-        self.module = self.URL_BASES['module'] + 'stats'
-        self.make_url(call_type='tokensupply')
+        self.url_dict[self.ACTION] = 'tokensupply'
+        self.url_dict[self.MODULE] = 'stats'
+        self.build_url()
         req = self.connect()
         return req['result']
 
     def get_token_balance(self, address):
-        self.address = self.URL_BASES['address'] + address
-        self.module = self.URL_BASES['module'] + 'account'
-        self.action = self.URL_BASES['action'] + 'tokenbalance'
-        self.make_url(call_type='tokenbalance')
+        self.url_dict[self.ADDRESS] = address
+        self.url_dict[self.MODULE] = 'account'
+        self.url_dict[self.ACTION] = 'tokenbalance'
+        self.build_url()
         req = self.connect()
         return req['result']