Intro to Flask Dynamic Routing

Learning objective: By the end of this lesson, students will be able to set up routes with parameters in Flask.

Dynamic Routing

We can define parameters for our routes with different routes being triggered based on where the data is passed.

We define route parameters using this syntax: <variable> - where variable is the name of the parameter that will be defined in the function where we want to access it.

Let’s add a third route to our app to demonstrate, only this route will be flexible based on the provided route parameter:

@app.route('/profile/<name>')
def profile(name):
    return f"This is the profile information for {name.upper()}"

if __name__ == '__main__':
    app.run()

Now, when you make requests to localhost:5000/profile/whatever, you should see the last section of the url included in the response message.

You can do anything you need to with that name variable. You can even pass dictionaries as parameters!

🚀 Check out the Flask docs for a deeper dive on routing.

🎓 You Do: Create a personnel route for an employee directory

In this exercise, we’ll want to provide users access to a simple data structure through a Flask route.

Users will make requests to /personnel/<name> and our Flask app will provide the information stored in a personnel dictionary about that person.

If there is no person with the requested name, return a 404 response. As always, consult the documentation for guidance on how to implement this.

personnel = {
    "rachel": "Executive Vice President of Managerial Functions",
    "wallace": "Senior Vice President of Managerial Functions",
    "rosie": "Staff Vice President of Managerial Functions",
    "james": "Vice Vice President of Managerial Functions",
    "henri": "Junior Vice President of Managerial Functions"
}

So, a request to localhost:5000/personnel/henri should provide a response of "Junior Vice President of Managerial Functions".

Query Parameters

Another effective way to pass additional information in a URL to a server is though query parameters. Query parameters are added to the end of a URL after a ? and are formatted as key=value pairs. In Express, these parameters are conveniently accessible through the req.query object.

For example, consider the following URL localhost:5000/employee-search?name=Christy&age=32.

This URL contains two query parameters:

name with a value of “Christy”
age with a value of “32”.

These parameters follow the ? symbol in the URL and are separated by &.

When a request is made to this URL, the server can retrieve these values from the request object.

We’ll need to add an import to the top of our app.py in order to access this object:

from flask import request

The request will then be able to access query parameters using a request.args.get() method, like so:

@app.route('/employee-search')
def employee_search():
    name = request.args.get('name')
    age = request.args.get('age')
    return f"I searched for employees named {name} who are {age} years old"

The name and age keys in the request object correspond to the query parameters in the URL. The server can then use this data, commonly for filtering results from a database.