title
Creating a Dynamic Select Field With Flask-WTF and JavaScript

description
In this video I show you how to create a dynamic (or dependent) select field using Flask-WTF and JavaScript along with the fetch function. After watching this video, you should be able to create your down drop downs that depend on others. Need one-on-one help with your project? I can help through my coaching program. Learn more here: https://prettyprinted.com/coaching Get the code here: https://prettyprinted.com/l/rFc Join my free course on the basics of Flask-SQLAlchemy: https://prettyprinted.com/flasksql Twitter: https://twitter.com/pretty_printed Github: https://github.com/prettyprinted

detail
{'title': 'Creating a Dynamic Select Field With Flask-WTF and JavaScript', 'heatmap': [{'end': 330.014, 'start': 313.703, 'weight': 0.818}, {'end': 396.8, 'start': 346.6, 'weight': 0.732}, {'end': 481.996, 'start': 467.19, 'weight': 0.818}, {'end': 683.831, 'start': 666.763, 'weight': 0.956}, {'end': 803.2, 'start': 784.267, 'weight': 0.771}], 'summary': "Tutorial 'creating a dynamic select field with flask-wtf and javascript' demonstrates how to create dependent dropdowns in flask wt forms, update city lists based on selected states, and dynamically process city data in python and javascript to achieve dynamic city dropdown options.", 'chapters': [{'end': 303.713, 'segs': [{'end': 111.566, 'src': 'embed', 'start': 82.473, 'weight': 0, 'content': [{'end': 88.896, 'text': "This is going to involve using a little bit of JavaScript and fetch, and we'll see how it works in just a moment.", 'start': 82.473, 'duration': 6.423}, {'end': 91.378, 'text': 'The first thing I want to do is I want to create a form.', 'start': 88.956, 'duration': 2.422}, {'end': 96.282, 'text': "So I will create a form and I'll just call this form.", 'start': 92.498, 'duration': 3.784}, {'end': 101.127, 'text': 'So this form is going to have both the state select and the city select.', 'start': 96.402, 'duration': 4.725}, {'end': 101.867, 'text': 'So the dropdowns.', 'start': 101.147, 'duration': 0.72}, {'end': 105.791, 'text': "So I need to inherit from flask form and then I'll create two.", 'start': 102.308, 'duration': 3.483}, {'end': 111.566, 'text': 'fields, so state and city.', 'start': 108.024, 'duration': 3.542}], 'summary': 'Creating a form with javascript and fetch for state and city dropdowns.', 'duration': 29.093, 'max_score': 82.473, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH082473.jpg'}, {'end': 237.036, 'src': 'embed', 'start': 208.698, 'weight': 1, 'content': [{'end': 214.202, 'text': "So what I'm going to do is I'm going to use form.city.choices.", 'start': 208.698, 'duration': 5.504}, {'end': 219.086, 'text': "So as you can see, I'm basically just modifying directly the choices here.", 'start': 214.803, 'duration': 4.283}, {'end': 223.693, 'text': 'and I need to have a list of tuples.', 'start': 221.293, 'duration': 2.4}, {'end': 226.714, 'text': "So what I'm going to do is I'm going to use a list comprehension.", 'start': 224.014, 'duration': 2.7}, {'end': 229.794, 'text': "And the first part I'll write is the query to get the data.", 'start': 227.134, 'duration': 2.66}, {'end': 237.036, 'text': "So it's going to be city.query.filterBy, and then I want to filter by the state equals CA.", 'start': 230.175, 'duration': 6.861}], 'summary': 'Using form.city.choices, modifying choices directly, using list comprehension, filtering data by state ca.', 'duration': 28.338, 'max_score': 208.698, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0208698.jpg'}], 'start': 0.751, 'title': 'Creating dependent dropdowns in flask', 'summary': 'Explains creating dependent dropdowns in flask wt forms or flask wtf and flask sql alchemy. it illustrates how one dropdown controls options in another with an example of states and cities. it includes code implementation and database querying.', 'chapters': [{'end': 303.713, 'start': 0.751, 'title': 'Creating dependent dropdowns in flask', 'summary': 'Explains how to create dependent dropdowns in flask wt forms or flask wtf and flask sql alchemy, illustrating the process of having one dropdown control the options in another dropdown with an example of states and cities. it includes code implementation and database querying.', 'duration': 302.962, 'highlights': ['Creating dependent dropdowns in Flask involves using JavaScript and fetch, and the process is demonstrated with an example of states and cities. The process of creating dependent dropdowns in Flask involves utilizing JavaScript and fetch to control the options in one dropdown based on the selection of another. The example demonstrates how to link the states and cities dropdowns together.', 'Demonstrating the process of initializing and populating a form with choices for the city dropdown based on the selected state, using list comprehension and querying the database. The chapter illustrates the process of initializing the city dropdown based on the selected state by using list comprehension to query the database for cities in a specific state and then populating the form with the retrieved choices.', 'The chapter explains the process of creating a form with state and city dropdowns, populating the state dropdown with predefined options and dynamically populating the city dropdown based on the selected state. It explains the creation of a form with two dropdowns, state and city, where the state dropdown is populated with predefined options, and the city dropdown is dynamically populated based on the selected state.']}], 'duration': 302.962, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0751.jpg', 'highlights': ['Creating dependent dropdowns in Flask involves using JavaScript and fetch, and the process is demonstrated with an example of states and cities.', 'The chapter illustrates the process of initializing the city dropdown based on the selected state by using list comprehension to query the database for cities in a specific state and then populating the form with the retrieved choices.', 'The chapter explains the process of creating a form with state and city dropdowns, populating the state dropdown with predefined options and dynamically populating the city dropdown based on the selected state.']}, {'end': 584.003, 'segs': [{'end': 396.8, 'src': 'heatmap', 'start': 313.703, 'weight': 4, 'content': [{'end': 317.726, 'text': 'Okay so, now that I have that, what I want to do is I want to render this template.', 'start': 313.703, 'duration': 4.023}, {'end': 319.107, 'text': 'So render template.', 'start': 317.906, 'duration': 1.201}, {'end': 322.669, 'text': 'And then I have an index.html template.', 'start': 319.707, 'duration': 2.962}, {'end': 325.491, 'text': "And I'll pass my form to that template.", 'start': 323.149, 'duration': 2.342}, {'end': 330.014, 'text': "And if I go to my index.html, you see I don't have much so far.", 'start': 325.971, 'duration': 4.043}, {'end': 333.756, 'text': "So what I'll do is I will create the form.", 'start': 330.975, 'duration': 2.781}, {'end': 335.898, 'text': 'Method equals post.', 'start': 334.957, 'duration': 0.941}, {'end': 340.021, 'text': "I don't need to put an action because it's going to be on the same endpoint.", 'start': 336.458, 'duration': 3.563}, {'end': 343.363, 'text': "And then I'll just use the form.", 'start': 341.001, 'duration': 2.362}, {'end': 346.5, 'text': 'variables that I have.', 'start': 345.7, 'duration': 0.8}, {'end': 358.625, 'text': 'So the cross site request forgery token is one and then the state is another and then the city is the last one.', 'start': 346.6, 'duration': 12.025}, {'end': 367.248, 'text': "I'll put just a really simple submit button here and then that should in my form.", 'start': 359.205, 'duration': 8.043}, {'end': 371.289, 'text': 'So everything looks good here.', 'start': 367.988, 'duration': 3.301}, {'end': 373.31, 'text': "So now what I'll do is I'll start up the app.", 'start': 371.629, 'duration': 1.681}, {'end': 379.645, 'text': "and I'll go to the page.", 'start': 377.922, 'duration': 1.723}, {'end': 382.289, 'text': 'Okay So we see, let me zoom in a bit.', 'start': 380.406, 'duration': 1.883}, {'end': 386.579, 'text': 'we see the drop down for California.', 'start': 383.638, 'duration': 2.941}, {'end': 392.34, 'text': 'So this select, I have California and Nevada, and then I have Los Angeles and San Diego here.', 'start': 386.639, 'duration': 5.701}, {'end': 396.8, 'text': 'And this Los Angeles and San Diego are generated by that query.', 'start': 392.68, 'duration': 4.12}], 'summary': 'Rendering index.html template with form variables for state and city, including california, nevada, los angeles, and san diego.', 'duration': 44.922, 'max_score': 313.703, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0313703.jpg'}, {'end': 536.524, 'src': 'heatmap', 'start': 467.19, 'weight': 0, 'content': [{'end': 474.166, 'text': 'id equals form city data and then give me the first result.', 'start': 467.19, 'duration': 6.976}, {'end': 476.89, 'text': "So let's see if that works as expected.", 'start': 474.607, 'duration': 2.283}, {'end': 481.996, 'text': "So California, Los Angeles, let's say I change this to San Diego and I hit submit query.", 'start': 478.231, 'duration': 3.765}, {'end': 485.581, 'text': 'I see State, CA, City, San Diego.', 'start': 482.497, 'duration': 3.084}, {'end': 490.545, 'text': "Okay, so that's almost Well, that's everything we need for the form itself.", 'start': 486.042, 'duration': 4.503}, {'end': 497.05, 'text': "But of course, when I change states, I don't have an updated list of cities.", 'start': 491.426, 'duration': 5.624}, {'end': 502.655, 'text': 'So like Nevada and Los Angeles, as far as I know, there is no Los Angeles in Nevada.', 'start': 497.15, 'duration': 5.505}, {'end': 511.462, 'text': 'So the important part of this is how do I get the code for switching this up? So there are two things that I need to do.', 'start': 502.995, 'duration': 8.467}, {'end': 520.058, 'text': 'I need to write some JavaScript to request for the additional cities and then update that list with the new cities.', 'start': 511.502, 'duration': 8.556}, {'end': 524.701, 'text': 'I also need to create a route in Flask to give me those cities.', 'start': 520.559, 'duration': 4.142}, {'end': 526.221, 'text': "I'll start with the route first.", 'start': 525.121, 'duration': 1.1}, {'end': 528.422, 'text': "I'll create a new route.", 'start': 527.582, 'duration': 0.84}, {'end': 534.423, 'text': "I'll call this city and I'll allow it to take a variable.", 'start': 529.522, 'duration': 4.901}, {'end': 536.524, 'text': 'The variable in this case is going to be a state.', 'start': 534.723, 'duration': 1.801}], 'summary': 'Transcript discusses updating city data based on state input using javascript and flask.', 'duration': 81.744, 'max_score': 467.19, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0467190.jpg'}], 'start': 303.713, 'title': 'Updating city list based on state in flask', 'summary': 'Covers updating the city list based on the selected state in a flask application, including the use of javascript to request additional cities, creating a flask route to retrieve and pass back the cities, and dynamically generating city options based on the selected state.', 'chapters': [{'end': 422.69, 'start': 303.713, 'title': 'Rendering form and submitting data', 'summary': 'Covers rendering a form template with cross-site request forgery token, state, and city variables and submitting the form data, including the functionality to dynamically generate city options based on the selected state.', 'duration': 118.977, 'highlights': ['The form template is rendered with cross-site request forgery token, state, and city variables, with the method set as post.', 'The city options are dynamically generated based on the selected state, such as California or Nevada, and change accordingly, such as displaying Los Angeles and San Diego for California, and Las Vegas and Reno for Nevada.']}, {'end': 584.003, 'start': 425.872, 'title': 'Updating city list based on state in flask', 'summary': 'Covers the process of updating the city list based on the selected state in a flask application, involving the use of javascript to request additional cities and updating the list, as well as creating a flask route to retrieve and pass back the cities for a specific state.', 'duration': 158.131, 'highlights': ['Creating a new route in Flask to retrieve cities based on the selected state The speaker describes the process of creating a new route in Flask to retrieve cities based on the selected state, involving querying the database for cities matching the specified state and passing the cities back as a response.', 'Using JavaScript to request additional cities and update the city list The chapter introduces the use of JavaScript to request additional cities and update the city list based on the selected state, demonstrating the need for dynamic updating of the cities based on the chosen state in the form.', 'Demonstrating the process of retrieving and displaying city information based on the selected state The speaker demonstrates the process of retrieving and displaying city information based on the selected state, emphasizing the need to have an updated list of cities when switching states within the form.']}], 'duration': 280.29, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0303713.jpg', 'highlights': ['The city options are dynamically generated based on the selected state, such as California or Nevada, and change accordingly, such as displaying Los Angeles and San Diego for California, and Las Vegas and Reno for Nevada.', 'Creating a new route in Flask to retrieve cities based on the selected state involving querying the database for cities matching the specified state and passing the cities back as a response.', 'Using JavaScript to request additional cities and update the city list based on the selected state demonstrating the need for dynamic updating of the cities based on the chosen state in the form.', 'Demonstrating the process of retrieving and displaying city information based on the selected state emphasizing the need to have an updated list of cities when switching states within the form.', 'The form template is rendered with cross-site request forgery token, state, and city variables, with the method set as post.']}, {'end': 1173.071, 'segs': [{'end': 610.548, 'src': 'embed', 'start': 585.325, 'weight': 0, 'content': [{'end': 591.21, 'text': "So now for each city, I'm going to do a little bit of processing, and then I'm going to append it to a master list.", 'start': 585.325, 'duration': 5.885}, {'end': 593.472, 'text': "So I'll call this master list city array.", 'start': 591.63, 'duration': 1.842}, {'end': 602.74, 'text': "and it's going to be initializes link and then what I'm going to do is loop over the cities that I got from the query.", 'start': 595.453, 'duration': 7.287}, {'end': 610.548, 'text': 'So for city in cities, what I want to do is create a new city object for each city.', 'start': 603, 'duration': 7.548}], 'summary': 'Processing data for each city and adding to master list.', 'duration': 25.223, 'max_score': 585.325, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0585325.jpg'}, {'end': 695.543, 'src': 'heatmap', 'start': 666.763, 'weight': 0.956, 'content': [{'end': 671.185, 'text': 'I need to pass a dictionary and I want the dictionary to be cities.', 'start': 666.763, 'duration': 4.422}, {'end': 674.446, 'text': "Then I'll pass in that city array just like that.", 'start': 671.245, 'duration': 3.201}, {'end': 680.409, 'text': "Now I'll go to this endpoint directly, so slash city slash NV.", 'start': 675.187, 'duration': 5.222}, {'end': 683.831, 'text': 'I see I have two cities here.', 'start': 681.39, 'duration': 2.441}, {'end': 687.994, 'text': 'The ID for Las Vegas is one, the ID for Reno is two.', 'start': 684.79, 'duration': 3.204}, {'end': 695.543, 'text': 'If I change Nevada NV to CA for California, I see I have Los Angeles and San Diego here.', 'start': 688.354, 'duration': 7.189}], 'summary': 'Pass a cities dictionary, with 2 cities for nv and 2 for ca.', 'duration': 28.78, 'max_score': 666.763, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0666763.jpg'}, {'end': 779.366, 'src': 'embed', 'start': 749.722, 'weight': 1, 'content': [{'end': 755.17, 'text': 'And I just need to get these two because I need a way to modify them.', 'start': 749.722, 'duration': 5.448}, {'end': 761.341, 'text': "So like I said, I want to trigger the change on the, so I'll go back.", 'start': 757.02, 'duration': 4.321}, {'end': 767.223, 'text': 'I want to trigger the change of these options whenever I change this option.', 'start': 762.201, 'duration': 5.022}, {'end': 771.044, 'text': 'So whenever I change the state drop-down, I want the cities to update.', 'start': 767.763, 'duration': 3.281}, {'end': 779.366, 'text': "So to do that, I'm going to put an on change listener on the state select, so state select.onchange.", 'start': 771.824, 'duration': 7.542}], 'summary': 'Implement onchange listener to update cities based on state dropdown selection.', 'duration': 29.644, 'max_score': 749.722, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0749722.jpg'}, {'end': 813.093, 'src': 'heatmap', 'start': 784.267, 'weight': 0.771, 'content': [{'end': 788.309, 'text': "Then inside of the function, what I'm going to do is I'm first going to get the value of the state.", 'start': 784.267, 'duration': 4.042}, {'end': 791.03, 'text': 'So state equals state select.value.', 'start': 788.629, 'duration': 2.401}, {'end': 796.712, 'text': "What I'll do is I'll alert the state so we can see that it appears correct.", 'start': 792.311, 'duration': 4.401}, {'end': 803.2, 'text': "So I'll refresh the page, And then now that I have the on change event, every time I change it, I get the alert.", 'start': 797.012, 'duration': 6.188}, {'end': 804.642, 'text': 'I see NV is here.', 'start': 803.46, 'duration': 1.182}, {'end': 807.506, 'text': 'If I change it back to California, I get CA.', 'start': 805.022, 'duration': 2.484}, {'end': 813.093, 'text': 'So I know the on change is working and I know I can actually get the value of the select box.', 'start': 807.726, 'duration': 5.367}], 'summary': 'Using javascript, the function retrieves and alerts the selected state value from a dropdown menu, demonstrating successful implementation.', 'duration': 28.826, 'max_score': 784.267, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0784267.jpg'}, {'end': 958.489, 'src': 'embed', 'start': 925.802, 'weight': 2, 'content': [{'end': 930.525, 'text': 'So now that I know that I have the data, what I want to do is I want to loop through all of the.', 'start': 925.802, 'duration': 4.723}, {'end': 935.004, 'text': 'the cities in the data.', 'start': 932.742, 'duration': 2.262}, {'end': 943.112, 'text': "so what i'll do is, i'll say for let's see, let's city of data dot cities.", 'start': 935.004, 'duration': 8.108}, {'end': 950.399, 'text': 'so i have an array of cities and this cities comes from the cities here from flask.', 'start': 943.112, 'duration': 7.287}, {'end': 958.489, 'text': "i'm going to loop over it And I want to construct some new HTML for the drop-down list.", 'start': 950.399, 'duration': 8.09}], 'summary': 'Loop through cities data to create new drop-down html.', 'duration': 32.687, 'max_score': 925.802, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0925802.jpg'}, {'end': 1063.621, 'src': 'embed', 'start': 1039.557, 'weight': 3, 'content': [{'end': 1046.885, 'text': 'quotes for the value and it has the city id and then the city name is going to be in between the option tags.', 'start': 1039.557, 'duration': 7.328}, {'end': 1054.833, 'text': 'and the very last thing i need to do is i need to update the city select to use this new option html instead of the old.', 'start': 1046.885, 'duration': 7.948}, {'end': 1063.621, 'text': "so to do that i'm going to use city select dot, inner html, and it's just going to be set equal to option html.", 'start': 1054.833, 'duration': 8.788}], 'summary': 'Updating city select with new option html.', 'duration': 24.064, 'max_score': 1039.557, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH01039557.jpg'}, {'end': 1128.444, 'src': 'embed', 'start': 1093.263, 'weight': 4, 'content': [{'end': 1095.865, 'text': "So as you can see, it's pretty easy in principle.", 'start': 1093.263, 'duration': 2.602}, {'end': 1099.968, 'text': 'There are some things you can add to this, of course.', 'start': 1097.306, 'duration': 2.662}, {'end': 1101.809, 'text': 'You can check for error cases.', 'start': 1100.208, 'duration': 1.601}, {'end': 1105.692, 'text': 'But I just wanted to keep this simple, just to keep the video short.', 'start': 1102.269, 'duration': 3.423}, {'end': 1108.854, 'text': 'But this is basically the process.', 'start': 1107.213, 'duration': 1.641}, {'end': 1111.015, 'text': "So finally, let's just see if it submits the data.", 'start': 1108.914, 'duration': 2.101}, {'end': 1116.138, 'text': 'So if I go to Nevada and then Reno, hit Submit Query, I see Nevada, City, Reno.', 'start': 1111.295, 'duration': 4.843}, {'end': 1120.52, 'text': 'If I use Nevada and then Las Vegas Submit, I see Las Vegas.', 'start': 1117.278, 'duration': 3.242}, {'end': 1128.444, 'text': 'If I go to Nevada and then come back to California and then go to San Diego, hit Submit, I see everything is working correctly.', 'start': 1121.32, 'duration': 7.124}], 'summary': 'Demonstrates simple process with successful data submissions in nevada and california.', 'duration': 35.181, 'max_score': 1093.263, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH01093263.jpg'}], 'start': 585.325, 'title': 'City data processing and dropdown list update', 'summary': 'Involves processing city data in python and setting up an on-change listener in javascript to update the city options based on the selected state. it also demonstrates updating a city dropdown list dynamically through a loop, appending new html options for each city displayed, and using inner html to update the dropdown list based on the selected state, resulting in a dynamic display of cities and their descriptions.', 'chapters': [{'end': 895.557, 'start': 585.325, 'title': 'Flask city data processing', 'summary': 'Involves processing city data in python and setting up an on-change listener in javascript to update the city options based on the selected state.', 'duration': 310.232, 'highlights': ['The chapter involves processing city data in Python by creating a master city array and appending a new city object for each city, with its ID and name, resulting in a JSONified version of the data.', "Setting up an on-change listener in JavaScript to trigger the change of city options whenever the state drop-down is modified, by fetching and transforming the response using JavaScript's fetch API and updating the city options accordingly."]}, {'end': 1173.071, 'start': 895.617, 'title': 'Updating city dropdown list', 'summary': 'Demonstrates how to update a city dropdown list dynamically through a loop, appending new html options for each city displayed, and using inner html to update the dropdown list based on the selected state, resulting in a dynamic display of cities and their descriptions.', 'duration': 277.454, 'highlights': ['The process involves dynamically updating the city dropdown list based on the selected state, achieved by looping through the cities data and constructing new HTML options for each city displayed. The process involves dynamically updating the city dropdown list based on the selected state, achieved by looping through the cities data and constructing new HTML options for each city displayed.', 'The demonstration showcases the usage of inner HTML to update the dropdown list with the newly constructed option HTML, resulting in a dynamic display of cities and their descriptions based on the selected state. The demonstration showcases the usage of inner HTML to update the dropdown list with the newly constructed option HTML, resulting in a dynamic display of cities and their descriptions based on the selected state.', 'The chapter emphasizes the simplicity of the process, highlighting the potential for enhancements such as error case handling and encourages viewers to access the code for modification and poses a link for further reference. The chapter emphasizes the simplicity of the process, highlighting the potential for enhancements such as error case handling and encourages viewers to access the code for modification and poses a link for further reference.']}], 'duration': 587.746, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/I2dJuNwlIH0/pics/I2dJuNwlIH0585325.jpg', 'highlights': ['The chapter involves processing city data in Python by creating a master city array and appending a new city object for each city, resulting in a JSONified version of the data.', "Setting up an on-change listener in JavaScript to trigger the change of city options whenever the state drop-down is modified, by fetching and transforming the response using JavaScript's fetch API and updating the city options accordingly.", 'The process involves dynamically updating the city dropdown list based on the selected state, achieved by looping through the cities data and constructing new HTML options for each city displayed.', 'The demonstration showcases the usage of inner HTML to update the dropdown list with the newly constructed option HTML, resulting in a dynamic display of cities and their descriptions based on the selected state.', 'The chapter emphasizes the simplicity of the process, highlighting the potential for enhancements such as error case handling and encourages viewers to access the code for modification and poses a link for further reference.']}], 'highlights': ['The chapter involves processing city data in Python by creating a master city array and appending a new city object for each city, resulting in a JSONified version of the data.', 'Creating dependent dropdowns in Flask involves using JavaScript and fetch, and the process is demonstrated with an example of states and cities.', 'The chapter illustrates the process of initializing the city dropdown based on the selected state by using list comprehension to query the database for cities in a specific state and then populating the form with the retrieved choices.', 'The process involves dynamically updating the city dropdown list based on the selected state, achieved by looping through the cities data and constructing new HTML options for each city displayed.', 'Using JavaScript to request additional cities and update the city list based on the selected state demonstrating the need for dynamic updating of the cities based on the chosen state in the form.']}