String: sequence of characters, immutable
ex. ‘hello’, s[i] is i th character in S
List: list of elements, mutable
ex. [‘alpha’, 23], p[i] is i th element of p
Dictionary: set of
ex. {‘hydrogen’: 1, ‘helium’: 23, d[k], k is whatever the key value
ex. d[k] = v, is similar to the update.
Here is a example to use dictionary
elements = {'hydrogen':1, 'helium':2, 'carbon':6 }
elements['lithimu'] = 3
elements['nitrogen'] = 8
elements['nitrogen'] = 7
print elements['nitrogen']
population = {'Shanghai':17.8, 'Istanbul':13.3, 'Karachi':13.0, 'Mumbai':12.5 }
another example
elements = {}
elements['H'] = {'name': 'Hydrogen', 'number': 1, 'weight': 1.00794}
elements['He'] = {'name': 'Helium', 'number': 2, 'weight': 4.002602, 'noble gas': True}
print elements['He']['name']
