>>> a = 'dave'
>>> a[3]

'e'

>>> a[4]

Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
IndexError: string index out of range

>>> a = 'dave'
>>> print a[0]
d
>>> a = ['d','a','v','e']
>>> print a[0]
d
>>> a = ('d','a','v','e')
>>> print a[0]
d

>>> s = 'dave'
>>> id(s)

140105068006304

>>> s = 'python' + s[1:]
>>> s

'pythonave'

>>> id(s)

140105067997536

>>> seq = 'dave'
>>> print seq[1:]

ave

>>> seq = ['d','a','v','e']
>>> print seq[1:]

['a', 'v', 'e']

>>> seq = ('d','a','v','e')
>>> print seq[1:]

('a', 'v', 'e')

>>> str = [ a * 2 for a in 'dave' ]
>>> print str

['dd', 'aa', 'vv', 'ee']

>>> L1 = [1,2,3]
>>> L2 = [4,5,6]
>>> L3 = [(a+b) for (a,b) in zip(L1,L2)]
>>> print L3

[5, 7, 9]

>>> tup = (1,2,3)
>>> tups = [ a * 2 for a in tup]
>>> print tups

[2, 4, 6]

>>> dic = {'a':'dave','b':'emily'}
>>> dics = [ i *2 for i in dic.items()]
>>> print dics

[('a', 'dave', 'a', 'dave'), ('b', 'emily', 'b', 'emily')]

>>> dic = {'a':'dave','b':'emily'}
>>> dicts = [ i * 2 for i in dic]
>>> print dicts

['aa', 'bb']

>>> a = [1,2,3]
>>> tup = (4,5,a)
>>> print tup[2]

[1, 2, 3]

>>> a[0] = 'x'
>>> print tup[2]

['x', 2, 3]

>>> a = '123'
>>> tup = (4,5,a)
>>> print tup[2]

123

>>> a = 'xxx'
>>> print tup[2]

123