Python Utility Functions

The following provides a list of Python utility functions that appeared throughout these documentations and that the developer may find useful for the Code step.

Generating Graphs

This utility function can be used to convert a matplotlib graph to an <img> HTML tag that can be embedded in the output page.

import matplotlib.pyplot as plt
import numpy as np
import base64
import io

def plt_show(plt, width=500, dpi=100):
    # Converts matplotlib plt to image data string
    #   plt is the matplotlib pyplot or figure
    #   width is the width of the graph image in pixels
    #   dpi (dots per inch) is the resolution of the image
    bytes = io.BytesIO()
    plt.savefig(bytes, format='png', dpi=dpi)  # Save as png image
    if hasattr(plt, "close"):
        plt.close()
    bytes.seek(0)
    base64_string = "data:image/png;base64," + \
        base64.b64encode(bytes.getvalue()).decode("utf-8")
    return "<img src='" + base64_string + "' width='" + str(width) + "'>"

def main(inputs):
    # Code to generate a plot using matplot lib (plt)
    # The following line uses the plt_show function to create an embeddable image
    img = plt_show(plt)
    return {"Image": img}

Text Files

This utility function can be used to generate a text file to be embedded in the output page using the <a> HTML tag, allowing the user to download it.

import base64

def Text_File(string,filename):
    # This function generates the required file_data string for download.
    # You can call this function to generate a text file containing the "string" data
    # filename provides the name of the file when the user attempts to download it.
    newdata = base64.b64encode(string.encode()).decode()
    extension = ".txt"
    meta = "data:text/plain;base64,"
    encoded_data = meta + newdata
    return "<a href='" + encoded_data + "' download='" + filename + extension + "'>Download File</a>"

def main(inputs):
    # code to generate the required string variable "t".
    t = ...
    File = Text_File(t, "MyFile")
    return {"File":File}

Image Files

This utility function can be used to generate an image file to be embedded in the output page using the <a> HTML tag, allowing the user to download it.

def Image_File(data, extension, filename):
    return "<a href='" + data + "' download='" + filename + "." + extension + "'>Download Image</a>"

def main(inputs):
    # code to generate encoded image file (encoded_data) and image format (extension).
    imagefile = Image_File(encoded_data,extension,"MyImage")
    return {
        # Download using <a> tags
        "File": imagefile,
    }

Displaying Images

This utility function can be used to generate an image file to be displayed in the output page using the <img> HTML tag.

def Image_Embed(data):
    return "<img src='" + data + "'>"

def main(inputs):
    #code to generate encoded image file (encoded_data)
    image = Image_Embed(encoded_data)
    return {
        # Display using <img> tag
        "Image": image,
    }

Generating Tables

This utility function generates a string using the <table> HTML tag that can be embedded in the output page to display a table. This utility routine works only with tables having more than one column.

def build_html_table(columns, column_headers):
    # <table> is the table
    # <tr> is table row
    # <th> is table header
    # <td> is table data cell
    # (1) Table opening table
    html_table = "<table border='3' cellpadding='5' style='border-collapse:collapse;'><tr>"
    # (2) Add header row
    rows = len(columns[0])
    for h in column_headers:
        html_table += "<th>" + h + "</th>"
    html_table += "</tr>"
    # (3) Add all data rows
    for i in range(rows):
        html_table += "<tr>"
        for column in columns:
            html_table += "<td>" + str(column[i]) + "</td>"
        html_table += "</tr>"
    # (4) Add the table closing tag
    html_table += "</table>"
    return html_table

def main(inputs):
    # Code to generate the arrays col1, col2, col3, ...
    columns = [col1,col2,col3,...]
    column_headers = ["Title 1", "Title 2","Title 3",...]
    table = build_html_table(columns,column_headers)
    return {"Table":table }