Add SDK documentation

Author: VadimGrznk

Readme.md

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+# Python ContractKit
+
+Celo's ContractKit is a library to help developers and validators to interact with the celo-blockchain.
+
+ContractKit supports the following functionality:
+
+- Connect to a node
+- Access web3 object to interact with node's Json RPC API
+- Send Transaction with celo's extra fields: (feeCurrency)
+- Simple interface to interact with CELO and cUSD
+- Simple interface to interact with Celo Core contracts
+- Utilities
+
+## User Guide
+
+### Getting Started
+
+To install:
+
+```bash
+pip install .
+```
+
+You need in Python version 3.8 or higher.
+
+To start working with python contractkit you need a `Kit` instance:
+
+```python
+from celo_sdk.kit import Kit
+
+kit = Kit('https://alfajores-forno.celo-testnet.org')
+```
+
+To access web3:
+
+```python
+kit.w3.eth.getBalance(some_address)
+```
+
+### Setting Default Tx Options
+
+`Kit` allows you to set default transaction options:
+
+```python
+from celo_sdk.kit import Kit
+
+kit = Kit('https://alfajores-forno.celo-testnet.org')
+currency_address = kit.base_wrapper.registry.load_contract_by_name('StableToken')['address']
+kit.wallet_fee_currency = currency_address
+```
+
+### Interacting with CELO & cUSD
+
+celo-blockchain has two initial coins: CELO and cUSD (stableToken).
+Both implement the ERC20 standard, and to interact with them is as simple as:
+
+```python
+gold_token = kit.base_wrapper.create_and_get_contract_by_name('GoldToken')
+balance = gold_token.balance_of(address)
+```
+
+To send funds:
+
+```python
+one_gold = kit.w3.toWei(1, 'ether')
+tx_hash = gold_token.transfer(address, one_gold)
+```
+
+To interact with cUSD, is the same but with a different contract:
+
+```python
+stable_token = kit.base_wrapper.create_and_get_contract_by_name('StableToken')
+```
+
+If you would like to pay fees in cUSD, set the gas price manually:
+
+```python
+stable_token = kit.base_wrapper.create_and_get_contract_by_name('StableToken')
+gas_price_contract = kit.base_wrapper.create_and_get_contract_by_name('GasPriceMinimum')
+gas_price_minimum = gas_price_contract.get_gas_price_minimum(stable.address)
+gas_price = gas_price_minimum * 1.3 # Wiggle room if gas price minimum changes before tx is sent
+kit.wallet_fee_currency = stable_token.address # Default to paying fees in cUSD
+kit.wallet_gas_price = gas_price
+
+tx = stable_token.transfer(recipient, wei_transfer_amount)
+```
+
+### Interacting with Other Contracts
+
+Apart from GoldToken and StableToken, there are many core contracts.
+
+For the moment, we have contract wrappers for:
+
+- Accounts
+- Attestations
+- BlockchainParameters
+- DoubleSigningSlasher
+- DowntimeSlasher
+- Election
+- LockedGold
+- Escrow
+- Exchange
+- Freezer
+- GasPriceMinimum
+- GoldToken
+- Governance
+- MultiSig
+- Reserve
+- ReleaseGold
+- SortedOracles
+- StableToken
+- Validators
+
+## A Note About Contract Addresses
+
+Celo Core Contracts addresses, can be obtained by looking at the `Registry` contract.
+That's actually how `BaseWrapper` obtain them.
+
+We expose the registry api, which can be accessed by:
+
+```python
+gold_token_address = kit.base_wrapper.registry.load_contract_by_name('GoldToken')['address']
+```
+
+## Adding new keys to the wallet
+
+Wallet object by defaut generate some private key
+
+But of course you can add your own already generated private key or generate new one
+
+To add your own:
+
+```python
+from celo_sdk.kit import Kit
+
+kit = Kit('https://alfajores-forno.celo-testnet.org')
+kit.wallet_add_new_key = '0xf2f48ee19680706196e2e339e5da3491186e0c4c5030670656b0e0164837257d'
+```
+
+To generate new one:
+
+```python
+new_key = kit.generate_new_key()
+kit.wallet_add_new_key = new_key
+```
+
+To see all the wallet accounts:
+
+```python
+accounts = kit.wallet.accounts
+```
+
+And to switch between accounts:
+
+```python
+kit.wallet_change_account = existing_account_address  # address of account has to be in wallet.__accounts dict
+```
+
+## Signing messages with wallet
+
+In addition to signing the transaction, the wallet can sign messages:
+
+```python
+from celo_sdk.kit import Kit
+
+kit = Kit('https://alfajores-forno.celo-testnet.org')
+signature = kit.wallet.sign_message(b'some message')
+```