Python Join Arguments and String Concatenation

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Problem: Write a function that joins an arbitrary number of string arguments with a given separator.

Example: Given the string arguments "A", "B", and "C" and the string separator "-". Join them to the concatenated string "A-B-C".

Solution: The following code creates a Python function concat() that takes an arbitrary number of arguments, packs them into the tuple args using the single asterisk operator, and joins the string arguments in args using the separator given as the final function argument. 

def concat(*args, sep="/"):
    return sep.join(args)

print(concat("hello", "world" sep=" "))
# hello world

Explanation: String concatenation is the process of creating a string by appending string arguments. The given function takes an arbitrary number of string arguments as specified by the *args keyword. The parameter sep declares the separator string to clue together two strings. The separator argument is a keyword argument because of the *args argument can have an arbitrary number of arguments. The keyword argument helps to differentiate whether the last parameter is part of *args or the sep argument.

The function concat is a wrapper for the join function to concatenate strings. The join function is defined in the string object sep. It concatenates an arbitrary number of strings using the separator to glue them together. Both functions achieve the same thing, but the first may be more convenient because the separator is a normal argument.

Yet, you will find yourself using the join function on a regular basis without writing your own wrapper functions. So you can as well learn its proper use now.

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