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.
"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
}
In Python, curly braces are used to define a dictionary.
a={'one':1, 'two':2, 'three':3}
a['one']=1
a['three']=3
In other languages, { } are used as part of the flow control. Python however used indentation as its flow control because of its focus on readable code.
for entry in entries:
code....
There's a little easter egg in Python when it comes to braces. Try running this on the Python Shell and enjoy.
from __future__ import braces
In languages like C curly braces ({}) are used to create program blocks used in flow control. In Python, curly braces are used to define a data structure called a dictionary (a key/value mapping), while white space indentation is used to define program blocks.
Dictionaries in Python are data structures that store key-value pairs. You can use them like associative arrays. Curly braces are used when declaring dictionaries:
d = {'One': 1, 'Two' : 2, 'Three' : 3 }
print d['Two'] # prints "2"
Curly braces are not used to denote control levels in Python. Instead, Python uses indentation for this purpose.
I think you really need some good resources for learning Python in general. See https://stackoverflow.com/q/175001/10077
A dictionary is something like an array that's accessed by keys (e.g. strings,...) rather than just plain sequential numbers. It contains key/value pairs, you can look up values using a key like using a phone book: key=name, number=value.
For defining such a dictionary, you use this syntax using curly braces, see also: http://wiki.python.org/moin/SimplePrograms
来源：https://stackoverflow.com/questions/9197324/what-is-the-meaning-of-curly-braces