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Formal parameters are mentioned in the function definition. Actual parameters(arguments) are passed during a function call. We can define a function with a variable number of arguments.
Example: In the below example, the default value is given to argument band c This function can be called in 3 ways
2. Giving one of the optional arguments. 3. Giving all the arguments Note: Default values are evaluated only once at the point of the function definition in the defining scope. So, it makes a difference when we pass mutable objects like a list or dictionary as default values. Functions can also be called using keyword arguments of the form kwarg=value. During a function call, values passed through arguments need not be in the order of parameters in the function definition. This can be achieved by keyword arguments. But all the keyword arguments should match the parameters in the function definition. Example: Calling the function add by giving keyword arguments
2. During a function call, only giving mandatory argument as a keyword argument. Optional default arguments are skipped. During a function call, values passed through arguments should be in the order of parameters in the function definition. This is called positional arguments. Keyword arguments should follow positional arguments only. Example: The above function can be called in two ways:
2. Giving a mix of positional and keyword arguments, keyword arguments should always follow positional arguments default vs positional vs keyword arguments: Important points to remember: Photo by Author1. default arguments should follow non-default arguments 2. keyword arguments should follow positional arguments 3. All the keyword arguments passed must match one of the arguments accepted by the function and their order is not important. 4. No argument should receive a value more than once 5. Default arguments are optional arguments Example 1: Giving only the mandatory arguments Example 2: Giving all arguments (optional and mandatory arguments) Variable-length arguments are also known as arbitrary arguments. If we don’t know the number of arguments needed for the function in advance, we can use arbitrary arguments Two types of arbitrary arguments
4. arbitrary positional arguments:For arbitrary positional argument, an asterisk (*) is placed before a parameter in function definition which can hold non-keyword variable-length arguments. These arguments will be wrapped up in a tuple. Before the variable number of arguments, zero or more normal arguments may occur. For arbitrary positional argument, a double asterisk (**) is placed before a parameter in a function which can hold keyword variable-length arguments. Example: As per the Python Documentation:
A function definition may look like: Photo by authorwhere / and * are optional. If used, these symbols indicate the kind of parameter by how the arguments may be passed to the function: positional-only, positional-or-keyword, and keyword-only.
1. Positional or keyword argumentsIf / and * are not present in the function definition, arguments may be passed to a function by position or by keyword 2. Positional only parameters Positional-only parameters are placed before a / (forward-slash) in the function definition. The / is used to logically separate the positional-only parameters from the rest of the parameters. Parameters following the / may be positional-or-keyword or keyword-only. If we specify keyword arguments for positional only arguments, it will raise TypeError. 3. Keyword only argumentsTo mark parameters as keyword-only, place an * in the arguments list just before the first keyword-only parameter. If we specify positional arguments for keyword-only arguments it will raise TypeError. All 3 calling conventions are used in the same function In the below-given example, the function add has all three arguments a,b — positional only arguments Important points to remember:
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