A Block is the fundamental part of the flow based programming philosophy of barfi. It can be considered as the building block that is used to build the data flow program. A Block has inputs, outputs and performs some computation. Any number of inputs and outputs can be added. Inputs and outputs are considered to be the interface to the Block, a connection. The inputs and outputs make up the connections to the other Blocks in the visual interface (the editor). The computation that each Block is to perform is to be specified when building the Block. When bluiding a Block, you only build a fundamental base Block. It is then considered that multiples/copies of these base Block are used to build the data flow.

Add picture of the block and the schema.

As a comparison to the common Node based programming, a Node is generally considered to perform a single specific computation. With barfi, a Block is considered to perform any type of computation, simple or complex.

Building a Block#

A Block here is a Python class object. That is built using the Block class in barfi.

from barfi import Block

Create your fundamental Block by giving it a name as:

my_block = Block(name='My Block')

Add an input interface to your Block, my_block as:


This creates an input interface with name Input 1, Input 2, and so. But if would like to add an input interface with a given name, use:

my_block.add_input(name='my input')

And, similarly you can add an output as:

my_block.add_output() # Creates an output with name: 'Output 1'
my_block.add_output(name='my output') # Creates an output with name: 'my output'

Adding a compute function to the Block

The idea of building a flow based program is to perform repeated computations using Blocks, and to customize the flow/program with the addition and/or removal of Blocks. Connections between the Blocks direct to how the program is executed and how data flows.

To add the computation function (ex. my_block_func) to your Block, make use of:


To execute this, you need to define your compute function (my_block_func). You need to pass in the argument self, as this function will be added as a method of your Block class. You can access/get the input interface values using self.get_interface(name='my input') with the name of the input. You can set the output interface values using self.set_interface(name= 'my output', value= my_output_value) with the name of the output interface and the value to be set.

def my_block_func(self):
    # get the value of the input interface
    in_1 = self.get_interface(name='input_1') 
    out_1 = (in_1/2) # ... perform come computation

    # get the value of the output interface
    self.set_interface(name='output_1', value=out_1)