I do not understand how this Python code works - Unknown programming concept
Question: My apologies for the crappy headline. If I were able to frame my problem
properly I would have used google ;)

I found an piece of python code able to parse ini files into a python dict
called "store":

    
    
    #!/usr/bin/env python
    
    from ConfigParser import SafeConfigParser
    
    def read(file, store):
    
        def parse_maybe(section):
            if not confp.has_section(section):
                return False
    
            if (section == "Main"):
                for left, right in confp.items(section):
                    store[left] = right.format(**store)
            return True
    
        confp = SafeConfigParser()
        confp.read(file)
        parse_maybe("Main")
    
    store = {}
    store["basedir"] = "/path/to/somewhere"
    read("foo.ini", store)
    

The ini files may include declarations with placeholders, for instance:

    
    
    [Main]
    output = {basedir}/somename.txt
    

When running the code, {basedir} gets replaced by "/path/to/somewhere" already
defined in store. I guess this magic comes from this line of code:

    
    
    store[left] = right.format(**store)
    

I understand _what_ the code does. But I do not understand _how_ this works.
What is this ** operator doing with the dictionary? A pointer to a tutorial,
etc. would be highly appreciated.


Answer: The answer to my question is twofold:

1) I did not know that this is possible with format:

    
    
    print "{a} is {b}".format(a="Python", b="great")
    

Python is great

2) Essentially the ** Operator unpacks a dictionary:

    
    
    dict = {"a": "Python", "b": "great"}
    print "{a} is {b}".format(**dict)
    

Python is great

