<center>![steem-python.png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1515886103/kmzfcpvtzuwhvqhgpyjp.png)</center>

This tutorial is part of a series where different aspects of programming with `steem-python` are explained. Links to the other tutorials can be found in the curriculum section below. This part will focus on how to analyse the `Steem Blockchain`. Instead of streaming `operations` as they are coming in, a custom starting point will be set with a custom time frame to collect data for.

---

#### What will I learn

- How does the Steem Blockchain work?
- Stream data starting from a custom block number
- What does an operation look like?
- Counting the amount of blocks analysed
- Filter operations and store statistics

#### Requirements

- Python3.6
- `steem-python`

#### Difficulty

- Intermediate

---

### Tutorial

#### Setup
Download the file from [Github](https://github.com/amosbastian/steempy-tutorials/tree/master/part_19). There is 1 file `analyse_blockchain.py` which contains the code. The file takes 1 argument from the command line which sets the amount of `blocks` to analyse.

Run scripts as following:
`> python analyse_blockchain.py 100`

####  How does the Steem blockchain work?
Every type of action on `Steem` is stored as an `operation` on the `Steem Blockchain`. These `operations` are stored in `blocks` which are created every 3 seconds in ascending order. Hence the name `blockchain`. The most recent block is the `head block`, while the rest of the chain is revered to as the tail.

```
from steem.blockchain import Blockchain

blockchain 		= Blockchain()
```
#### Stream data starting from a custom block number
Until now all tutorials which applied streaming the `blockchain` worked with new blocks that were coming in. However, it is also possible to start from a `custom block number` and work from there. This is useful when you want to look back and analyse blocks. For obtaining the current `head block` the following function can be called.

```
blockchain.get_current_block_num()
```
<br>
This script will look back a custom amount of `blocks` into time from the current `head block`.

```
start_block		= head_block - <amount of blocks to analyse>
```
<br>
The stream can be created with the following function, where `start_block` defines the starting point in the `blockchain`.

```
stream 			= blockchain.stream_from(start_block=start_block)
```
<br>
**New blocks are generated every 3 seconds. Analysing 1 day therefore sums up to 24x60x20 = 28 800 blocks**

#### What does an operation look like?
One block can contain multiple operation, like the one below.

```
{
	'trx_id': '6a49a53070279a59ade771d8573800afa9d38f2e',
	'block': 19424314,
	'trx_in_block': 0,
	'op_in_trx': 0,
	'virtual_op': 0,
	'timestamp': '2018-01-30T06:53:57',
	'op': ['transfer', {
		'from': 'minnowbooster',
		'to': 'elizzium2018',
		'amount': '0.002 SBD',
		'memo': 'You got an upgoat worth roughly 0.44$ in post rewards that will be done by blockchainttmft. We detected an open value of 0.005 SBD, worth 0.002 SBD in send and refunded that. '
	}]
}
```

`op` designates what kind `operation` was used . There are over 30 different kind of `operations`.

#### Counting the amount of blocks analysed
The time frame will the amount of `blocks` to be analysed. Since 1 block can contain multiple
`operations` counting the amount of `operations` will not work. The `block number` in which the operation is stored can be used to determine if a new `block` has been reached.

```
current_block 	= start_block
counter					= 0

for post in stream:
		if post['block'] != current_block:
			counter += 1
			print ("Block {}/{} {:.2f}%".format(counter, block_count, counter/block_count*100))
			current_block = post['block']
```

#### Filter operations and store statistics

To count the amount of each unique `operation` a `dict` is made, in this `dict` each `operation` is stored as a `key pair` with the amount of occurrences.
```
stats 			= {}
operation 	= post['op'][0]

if operation not in stats:
	stats[operation] = 1
else:
	stats[operation] += 1
```

#### Running the script
Running the script will analyse the set amount of `blocks` back in time from the current `head block`. Depending on the amounts of `blocks` to be analysed this can take some time.

```
python analyse_blockchain.py 28800
...
Block 28797/28800 99.99%
Block 28798/28800 99.99%
Block 28799/28800 100.00%
Block 28800/28800 100.00%

operations 1836907

custom_json 350000
vote 710553
claim_reward_balance 59814
comment 281821
transfer 48456
producer_reward 28800
curation_reward 166849
comment_benefactor_reward 11297
author_reward 57549
...
```



#### Curriculum
##### Set up:
- [Part 0: How To Install Steem-python, The Official Steem Library For Python](https://utopian.io/utopian-io/@amosbastian/how-to-install-steem-python-the-official-steem-library-for-python)
- [Part 1: How To Configure The Steempy CLI Wallet And Upvote An Article With Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-1-how-to-configure-the-steempy-cli-wallet-and-upvote-an-article-with-steem-python)
##### Filtering
- [Part 2: How To Stream And Filter The Blockchain Using Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-2-how-to-stream-and-filter-the-blockchain-using-steem-python)
- [Part 6: How To Automatically Reply To Mentions Using Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-6-how-to-automatically-reply-to-mentions-using-steem-python)
##### Voting
- [Part 3: Creating A Dynamic Autovoter That Runs 24/7](https://utopian.io/utopian-io/@steempytutorials/part-3-creating-a-dynamic-upvote-bot-that-runs-24-7-first-weekly-challenge-3-steem-prize-pool)
- [Part 4: How To Follow A Voting Trail Using Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-4-how-to-follow-a-voting-trail-using-steem-python)
- [Part 8: How To Create Your Own Upvote Bot Using Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-8-how-to-create-your-own-upvote-bot-using-steem-python)
##### Posting
- [Part 5: Post An Article Directly To The Steem Blockchain And Automatically Buy Upvotes From Upvote Bots](https://utopian.io/utopian-io/@steempytutorials/part-5-post-an-article-directly-to-the-steem-blockchain-and-automatically-buy-upvotes-from-upvote-bots)
- [Part 7: How To Schedule Posts And Manually Upvote Posts For A Variable Voting Weight With Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-7-how-to-schedule-posts-and-manually-upvote-posts-for-a-variable-voting-weight-with-steem-python)
###### Constructing
- [Part 10: Use Urls To Retrieve Post Data And Construct A Dynamic Post With Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-10-use-urls-to-retrieve-post-data-and-construct-a-dynamic-post-with-steem-python)
##### Rewards
- [Part 9: How To Calculate A Post's Total Rewards Using Steem-Python](https://utopian.io/utopian-io/@steempytutorials/how-to-calculate-a-post-s-total-rewards-using-steem-python)
- [Part 12: How To Estimate Curation Rewards Using Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-12-how-to-estimate-curation-rewards)
- [Part 14: How To Estimate All Rewards In Last N Days Using Steem-Python](https://utopian.io/utopian-io/@steempytutorials/how-to-estimate-all-rewards-in-last-n-days-using-steem-python)
##### Transfers
- [Part 11: How To Build A List Of Transfers And Broadcast These In One Transaction With Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-11-how-to-build-a-list-of-transfers-and-broadcast-these-in-one-transaction-with-steem-python)
- [Part 13: Upvote Posts In Batches Based On Current Voting Power With Steem-Python](https://utopian.io/utopian-io/@steempytutorials/part-13-upvote-posts-in-batches-based-on-current-voting-power-with-steem-python)
##### Account Analysis
- [Part 15: How To Check If An Account Is Following Back And Retrieve Mutual Followers/Following Between Two Accounts](https://utopian.io/utopian-io/@steempytutorials/part-15-how-to-check-if-an-account-is-following-back-and-retrieve-mutual-followers-following-between-two-accounts)
- [Part 16: How To Analyse A User's Vote History In A Specific Time Period Using Steem-Python](https://steemit.com/utopian-io/@steempytutorials/part-16-how-to-analyse-a-user-s-vote-history-in-a-specific-time-period-using-steem-python)
- [Part 18: How To Analyse An Account's Resteemers Using Steem-Python](https://steemit.com/utopian-io/@steempytutorials/part-18-how-to-analyse-an-account-s-resteemers)
---

The code for this tutorial can be found on [GitHub](https://github.com/amosbastian/steempy-tutorials/tree/master/part_19)!

This tutorial was written by @juliank in conjunction with @amosbastian.

<br /><hr/><em>Posted on <a href="https://utopian.io/utopian-io/@steempytutorials/part-19-analysing-the-steem-blockchain-for-a-custom-block-number-for-a-custom-block-count">Utopian.io -  Rewarding Open Source Contributors</a></em><hr/>