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Editor to share with you how python uses default values in function declarations. I believe most people don't know much about it, so share this article for your reference. I hope you can learn a lot after reading this article. Let's learn about it together.

Use default values in function declarations

In almost all Python projects, most of the code involves creating and calling functions. In other words, we are constantly dealing with function declarations and refactoring. In many cases, we need to call a function multiple times. This feature will vary slightly depending on the parameter set. However, sometimes one set of parameters may be more commonly used than the other, in which case we should consider setting the default value when declaring the function. Consider the following simple example.

# The original form: def generate_plot (data, image_name): "This function creates a scatter plot for the data"# create the plot based on the data... If image_name: # save the image... # In many cases, we don't need to save the image generate_plot (data, None) # The one with a default value def generate_plot (data, image_name=None): pass# Now, we can omit the second parameter generate_plot (data)

One thing to note is that if you want to deal with variable data types (such as lists, collections) when setting default values, be sure to use None instead of constructors (for example, arg_name = []). Because Python creates the function object at the defined location, the blank list provided will be "stuck" by the function object. In other words, the function object is not created immediately when it is called. Instead, we will process the same function object in memory, including the default mutable object it originally created, which can lead to unexpected behavior.

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