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What is the meaning of curly braces?


Just starting to figure Python out. I've read this question and its responses:

Is it true that I can't use curly braces in Python?

and I still can't fathom how curly braces work, especially since pages like Simple Programs:

http://wiki.python.org/moin/SimplePrograms

use curly braces all over the place. I understand square brackets and regular curved parentheses, but I don't know what's meant by "defining dictionaries" or what they're supposed to represent.


Solution

  • "Curly Braces" are used in Python to define a dictionary. A dictionary is a data structure that maps one value to another - kind of like how an English dictionary maps a word to its definition.

    Python:

    dict = {
        "a" : "Apple",
        "b" : "Banana",
    }
    

    They are also used to format strings, instead of the old C style using %, like:

    ds = ['a', 'b', 'c', 'd']
    x = ['has_{} 1'.format(d) for d in ds]
    
    print x
    
    ['has_a 1', 'has_b 1', 'has_c 1', 'has_d 1']
    

    They are not used to denote code blocks as they are in many "C-like" languages.

    C:

    if (condition) {
        // do this
    }
    

    Update: In addition to Python's dict data types Python has (since Python 2.7) set as well, which uses curly braces too and are declared as follows:

    my_set = {1, 2, 3, 4}