How to pass parameters in Flask

Flask is a popular web framework for Python that allows you to create dynamic web applications with minimal code. One of the features of Flask is that you can pass parameters to your routes using either query strings or path parameters. We will explore how to do both and when to use them.

Query strings are the part of the URL that comes after the question mark (?). They are composed of key-value pairs separated by ampersands (&). For example, in the URL, the query string is summary=VVV&change=Feauure, and it has two parameters: summary and change.

To access the query string parameters in Flask, you can use the request.args object, which is a dictionary-like object that contains all the parameters and their values. For example, you can write a route like this:

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def createcm():
summary = request.args.get(‘summary’)
change = request.args.get(‘change’)
# do something with summary and change
return ‘success’

The request.args.get() method returns the value of the parameter if it exists, or None if it does not. You can also provide a default value as a second argument, for example: summary = request.args.get(‘summary’, ‘default summary’).

Query strings are useful when you want to pass optional or non-essential parameters to your route, such as filters, sorting options, or pagination. They are also easy to manipulate by the user, so you should not use them for sensitive or critical data.

Path parameters are the parts of the URL that are enclosed in angle brackets (< >). They are placeholders for dynamic values that are part of the resource identifier. For example, in the URL, the path parameters are VVV and Feauure.

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To use path parameters in Flask, you need to include them in your route definition and your function signature. For example, you can write a route like this:


def createcm(summary, change):
# do something with summary and change
return ‘success’

The path parameters are passed as arguments to your function, and you can access them by their names. You can also specify the type of the parameter by adding a colon (:) after the parameter name, for example: or . This will validate the parameter and convert it to the specified type.

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Path parameters are useful when you want to pass essential or unique parameters to your route, such as identifiers, names, or slugs. They are also more semantic and RESTful than query strings, as they reflect the hierarchy and structure of your resources.

Flask provides two ways to pass parameters to your routes: query strings and path parameters. You should use query strings for optional or non-essential parameters, and path parameters for essential or unique parameters. Both methods have their advantages and disadvantages, and you should choose the one that suits your use case best.