How to Effectively Pass Variables Between Flask Pages?

Passing Variables Between Flask Pages

When navigating between routes in a Flask application, there may be a need to pass variables from one page to another for reuse. This article explores the different ways to accomplish this task, providing comprehensive solutions for both server-side and client-side scenarios.

Server-Side Techniques:

1. Session:

   • For private data not visible to the user, sessions offer a secure way to store temporary information server-side.
   • The session behaves like a dictionary, allowing storage of any JSON-serializable data.

   • Example:

     # Page A
     session['my_var'] = 'my_value'
     return redirect(url_for('b'))
     
     # Page B
     # ...
     my_var = session.get('my_var', None)

Client-Side Techniques:

1. Query Parameters:

   • Pass value from a template using query parameters, which are appended to the URL.
   • The retrieved value remains hidden to the end-user.

   • Example:

     <!-- Page A -->
     <a href="{{ url_for('b', my_var='my_value') }}">Send my_value</a>
     
     <!-- Page B -->
     # ...
     my_var = request.args.get('my_var', None)

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