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| This page shows how you can get datatokens & download an asset |
Consume flow
We assumed that you accomplished the publish flow presented previously.
Now let's see how can Bob get access to Alice's asset in order to download/consume it.
Get access for a dataset 🔑
Below, we show four possible approaches:
- A & B are when Alice is in contact with Bob. She can mint directly to him, or mint to herself and transfer to him.
- C is when Alice wants to share access for free, to anyone
- D is when Alice wants to sell access
In the same Python console:
from ocean_lib.ocean.util import to_wei
#Approach A: Alice mints datatokens to Bob
datatoken.mint(bob, to_wei(1), {"from": alice})
#Approach B: Alice mints for herself, and transfers to Bob
datatoken.mint(alice, to_wei(1), {"from": alice})
datatoken.transfer(bob, to_wei(1), {"from": alice})
#Approach C: Alice posts for free, via a dispenser / faucet; Bob requests & gets
datatoken.create_dispenser({"from": alice})
datatoken.dispense(to_wei(1), {"from": bob})
#Approach D: Alice posts for sale; Bob buys
# D.1 Alice creates exchange
price = to_wei(100)
exchange = datatoken.create_exchange({"from": alice}, price, ocean.OCEAN_address)
# D.2 Alice makes 100 datatokens available on the exchange
datatoken.mint(alice, to_wei(100), {"from": alice})
datatoken.approve(exchange.address, to_wei(100), {"from": alice})
# D.3 Bob lets exchange pull the OCEAN needed
OCEAN_needed = exchange.BT_needed(to_wei(1), consume_market_fee=0)
ocean.OCEAN_token.approve(exchange.address, OCEAN_needed, {"from":bob})
# D.4 Bob buys datatoken
exchange.buy_DT(to_wei(1), consume_market_fee=0, tx_dict={"from": bob})
For more info, check Technical Details about ocean.py most used functions and also the smart contracts for Dispenser & Fixed Rate Exchange.
Consume the asset ⬇️
To "consume" an asset typically means placing an "order", where you pass in 1.0 datatokens and get back a url. Then, you typically download the asset from the url.
Bob now has the datatoken for the dataset! Time to download the dataset and use it.
In the same Python console:
# Bob sends a datatoken to the service to get access
order_tx_id = ocean.assets.pay_for_access_service(ddo, {"from": bob})
# Bob downloads the file. If the connection breaks, Bob can try again
asset_dir = ocean.assets.download_asset(ddo, bob, './', order_tx_id)
import os
file_name = os.path.join(asset_dir, "file0")
Let's check that the file is downloaded. In a new console:
cd my_project/datafile.did:op:*
cat file0
The beginning of the file should contain the following contents:
% 1. Title: Branin Function
% 3. Number of instances: 225
% 6. Number of attributes: 2
@relation branin
@attribute 'x0' numeric
@attribute 'x1' numeric
@attribute 'y' numeric
@data
-5.0000,0.0000,308.1291
-3.9286,0.0000,206.1783
...