Product Perfect

DASH is not a programming language in itself, but rather an acronym for various technologies and concepts in the field of computer science. However, there's Dash scripting language which is a Unix shell that's usually used as a faster alternative to the Bourne Again Shell (Bash). It's known for its efficiency and limited features compared to other shells. On another note, there’s also Dash by Plotly which is an open-source Python framework used for building analytical web applications. It’s particularly useful for data scientists who need to create data visualizations or dashboards without having to know front-end technologies like HTML, CSS, and JavaScript.

Ask the right questions secure the right DASH talent among an increasingly shrinking pool of talent.

First 20 minutes

General DASH app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in DASH application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you install DASH?

You can install DASH using pip, a package manager for Python. The command is 'pip install dash'.

What are the main components of DASH?

The main components of DASH are Dash HTML Components, Dash Core Components, and Dash DataTable.

How would you create a simple DASH application?

To create a simple DASH application, you would first import the necessary libraries, then define the layout of the application using HTML and DASH components, and finally run the application using the 'run_server' method.

What is the purpose of the 'app.layout' in DASH?

The 'app.layout' in DASH is where you define the layout of the application. It describes what the application looks like.

Describe the difference between 'dash_html_components' and 'dash_core_components'.

'dash_html_components' is a library that provides classes for all HTML tags, while 'dash_core_components' is a library that provides higher level components like controls and graphs.

The hiring guide has been successfully sent to your email address.

Oops! Something went wrong while submitting the form.

What you’re looking for early on

Does the candidate have a strong understanding of DASH?

Has the candidate demonstrated problem-solving skills?

Is the candidate able to communicate effectively?

Does the candidate have experience with other relevant technologies?

Next 20 minutes

Specific DASH development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you handle user input in DASH?

User input in DASH can be handled using callbacks. Callbacks are functions that are automatically called by DASH whenever an input property changes.

What are 'State' and 'Event' in DASH callbacks?

'State' and 'Event' are two types of arguments that can be passed to DASH callbacks. 'State' represents the current state of a component, while 'Event' represents a user interaction with the component.

How would you update a graph in DASH in response to user input?

You can update a graph in DASH in response to user input by defining a callback that takes the user input as an input argument and returns a new figure for the graph.

What is the purpose of the 'dash.dependencies.Input' and 'dash.dependencies.Output' in DASH?

'dash.dependencies.Input' and 'dash.dependencies.Output' are used to define the inputs and outputs of a callback in DASH. The 'Input' specifies the component and property that should trigger the callback, while the 'Output' specifies the component and property that should be updated by the callback.

Describe the difference between 'clientside callbacks' and 'serverside callbacks' in DASH.

'Clientside callbacks' are executed in the browser using JavaScript, while 'serverside callbacks' are executed on the server using Python. 'Clientside callbacks' can improve performance by reducing server load and network latency.

The hiring guide has been successfully sent to your email address.

Oops! Something went wrong while submitting the form.

At this point, a skilled DASH engineer should demonstrate strong problem-solving abilities, proficiency in DASH programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with DASH.

What does the following simple DASH code do?
import dash
import dash_core_components as dcc
import dash_html_components as html

app = dash.Dash(__name__)

app.layout = html.Div(children=[
    html.H1(children='Hello Dash'),
    html.Div(children='''
        Dash: A web application framework for Python.
    '''),
])

if __name__ == '__main__':
    app.run_server(debug=True)
This code creates a simple Dash web application with a heading 'Hello Dash' and a paragraph 'Dash: A web application framework for Python.'
What will be the output of the following DASH code snippet?
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Input(id='my-id', value='initial value', type='text'),
    html.Div(id='my-div')
])

@app.callback(
    Output(component_id='my-div', component_property='children'),
    [Input(component_id='my-id', component_property='value')]
)
def update_output_div(input_value):
    return 'You've entered \'{}\''.format(input_value)

if __name__ == '__main__':
    app.run_server(debug=True)
This code creates a Dash web application with a text input field and a div. Whatever is typed into the text input field will be displayed in the div with the prefix 'You've entered'.
What does the following DASH code do that involves manipulating a list?
import dash
import dash_core_components as dcc
import dash_html_components as html

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Dropdown(
        id='my-dropdown',
        options=[
            {'label': 'New York City', 'value': 'NYC'},
            {'label': 'Montreal', 'value': 'MTL'},
            {'label': 'San Francisco', 'value': 'SF'}
        ],
        value='NYC'
    ),
    html.Div(id='output-container')
])
This code creates a Dash web application with a dropdown menu. The options for the dropdown menu are 'New York City', 'Montreal', and 'San Francisco'. The default selected value is 'New York City'.
What does the following DASH code do that involves threading?
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output
import time

app = dash.Dash(__name__)

app.layout = html.Div([
    html.Button('Execute Long Process', id='button'),
    html.Div(id='output-container-button')
])

@app.callback(
    Output('output-container-button', 'children'),
    [Input('button', 'n_clicks')]
)
def update_output(n_clicks):
    if n_clicks is not None:
        time.sleep(5)
        return 'Completed process'
This code creates a Dash web application with a button. When the button is clicked, it triggers a long process that lasts for 5 seconds (simulated with time.sleep(5)) and then displays 'Completed process'.

Wrap-up questions

Final candidate for DASH Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle DASH application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

How would you handle errors in DASH callbacks?

Errors in DASH callbacks can be handled using Python's standard error handling mechanisms, such as try/except blocks. DASH also provides a 'dash.exceptions.PreventUpdate' exception that can be raised to prevent a callback from updating its output.

What is the purpose of the 'dash.dependencies.State' in DASH?

'dash.dependencies.State' is used to pass extra values into a callback without triggering the callback. It represents the current state of a component.

How would you create a multi-page application in DASH?

You can create a multi-page application in DASH by defining a layout with a 'dcc.Location' component and a 'html.Div' component, and then defining a callback that updates the 'html.Div' component based on the current path in the 'dcc.Location' component.

DASH application related

Product Perfect's DASH development capabilities

Beyond hiring for your DASH engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in DASH projects, and can engage in multiple capacities.

DASH Consultive assessments

DASH Application Conversion Assessment DASH Application Integration Assessment DASH Data & Database Integration Assessment

Custom DASH development projects

Custom DASH App Conversion DASH Custom App Development Process App UI Design for DASH Facelifts

Hiring guide for DASH Engineers

DASH Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the DASH engineer at this point.

DASH Consultive assessments

Custom DASH development projects