In the below example, I would expect all the elements to be tuples. Why is a tuple converted to a string when it only contains a single string?
>>> a = [('a'), ('b'), ('c', 'd')]
>>> a
['a', 'b', ('c', 'd')]
>>>
>>> for elem in a:
... print type(elem)
...
<type 'str'>
<type 'str'>
<type 'tuple'>
why is a tuple converted to a string when it only contains a single string?
a = [('a'), ('b'), ('c', 'd')]
Because those first two elements aren't tuples; they're just strings. The parenthesis don't automatically make them tuples. You have to add a comma after the string to indicate to python that it should be a tuple.
>>> type( ('a') )
<type 'str'>
>>> type( ('a',) )
<type 'tuple'>
To fix your example code, add commas here:
>>> a = [('a',), ('b',), ('c', 'd')]
^ ^
From the Python Docs:
A special problem is the construction of tuples containing 0 or 1 items: the syntax has some extra quirks to accommodate these. Empty tuples are constructed by an empty pair of parentheses; a tuple with one item is constructed by following a value with a comma (it is not sufficient to enclose a single value in parentheses). Ugly, but effective.
If you truly hate the trailing comma syntax, a workaround is to pass a list to the tuple() function:
x = tuple(['a'])
tuple accepts an iterable, which a string is (iterates over characters). If you insist on not using the trailing comma, then make an intermediate list: tuple(['abc']).Your first two examples are not tuples, they are strings. Single-item tuples require a trailing comma, as in:
>>> a = [('a',), ('b',), ('c', 'd')]
>>> a
[('a',), ('b',), ('c', 'd')]
('a') is not a tuple, but just a string.
You need to add an extra comma at the end to make python take them as tuple: -
>>> a = [('a',), ('b',), ('c', 'd')]
>>> a
[('a',), ('b',), ('c', 'd')]
>>>
=> If you need to convert list to tuple which have one id as a element. then this solution will help you.
x_list = [1]
x_tuple = tuple(x_list)
=> You will get this
(1,)
=> so now append 0 into list and then convert it into tuple
=> x_list.append(0)
=> x_tuple = tuple(x_list)
(1, 0)
Came across this page and I was surprised why no one mentioned one of the pretty common method for tuple with one element. May be this is version thing since this is a very old post. Anyway here it is:
>>> b = tuple(('a'))
>>> type(b)
<class 'tuple'>
(foo,) didn't work for me)
tuple(('ab')) and the result will be ('a', 'b') instead of ('ab',).
tuple([var])
('a')just evaluates to'a',:a = 1, 2, 3; print a(), which only consists in a pair of parentheses.False- just about all an empty tuple is good for (if you see what I mean).