PY: Get Delegations By User

Full, runnable src of Get Delegations By User can be downloaded as part of the PY tutorials repository.

In this tutorial we will explain and show you how to pull a list of both active and expiring vesting delegations from the Steem blockchain using the steem class found within the steem-python library.

Intro

The Steem python library has a built-in function to pull information from the blockchain. We are using the get_vesting_delegations and get_expiring_vesting_delegations methods found within the steem class in the library. Each of these functions are executed separately. It should be noted that when a delegation is cancelled the VESTS will only be available again after 7 days. The value of the delegation can also be changed at any time, either decreased or increased. To get active delegations we need the following parameters:

1. account - The user account that the delegation list is being queried for
2. from-account - The account name from where to start the search. This parameter can be left empty to pull a list from the first delegatee
3. limit - The maximum amount of delegations that will be returned by the query

The function to query the expiring delegations use the the same parameters except that the start_account is replaced by a start_date. If this value is greater than 7 days from present, it will always include all delegations that are pending expiration.

Steps

1. App setup - Library install and import. Connection to production
2. User input - Input user and limit parameters
3. Delegation lists - Selection of the type of list and blockchain query

1. App setup

In this tutorial we use 2 package:

• steem - steem-python library and interaction with Blockchain
• pick - helps select the query type interactively

We import the libraries and connect to the production server.

from pick import pick
from steem import Steem

import pprint

client = Steem()

pprint is used to print the query results in an easier to read format

2. User input

The account and limit parameters are assigned via input from the console/terminal. We also check if the username provided does in fact exist on the blockchain using the get_account method also found within the steem class. This will return an null value if the name does not exist.

#capture username
username = input('Username: ')

#check username
result = client.get_account(username)
if not result:
	print('Invalid username')
	exit()

#capture list limit
limit = input('Max number of vesting delegations to display: ')

3. Delegation lists

We use two different functions to query active and expiring delegations, so the user is given a choice on which of these lists he wants to view.

#list type
title = 'Please choose the type of list: '
options = ['Active Vesting Delegations', 'Expiring Vesting Delegations']

#get index and selected list name
option, index = pick(options, title)
print('\n' + 'List of ' + option + ': ' + '\n')

Based on the result of the choice, the relevant blockchain query is executed and the result of the query displayed on the console/terminal.

if option=='Active Vesting Delegations' :
    #active delegations
	delegations = client.get_vesting_delegations(username, '', limit)
	if len(delegations) == 0:
		print('No ' + option)
	else:
		pprint.pprint(delegations)
else:
    #expiring delegations
	delegations = client.get_expiring_vesting_delegations(username, "2018-01-01T00:00:00", limit)
	if len(delegations) == 0:
		print('No ' + option)
	else:
		pprint.pprint(delegations)

For both the queries the starting points were defined in such a way as to include all available data but this can be changed depending on the user requirements.

That’s it!

To Run the tutorial

1. review dev requirements
2. clone this repo
3. cd tutorials/29_get_delegations_by_user
4. pip install -r requirements.txt
5. python index.py
6. After a few moments, you should see a prompt for input in terminal screen.