Adding all the numbers from a list together(not summing). Python 3.3.2 [duplicate]

Answer 1

You can use ''.join() in conjunction with map():

>>> alist = [2, 0, 1]
>>> ''.join(map(str, alist))
'201'

Answer 2

The string join function needs a list of strings.

''.join([str(i) for i in alist])

Answer 3

Is this what you're looking for?

hahaha = ''.join([str(num) for num in alist])
print hahaha  # '201'

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To explain what's going on:

The portion [str(num) for num in alist] is called a "list comprehension" -- it's like a very condensed for-loop that transforms one list into another list. In this case, it turns [2, 0, 1] into ['2', '0', '1'].

(We could, of course, write this as a for-loop instead of as a list comprehension, but it take more lines of code, and would be a little tedious to type)

The section portion ''.join(list) takes a list of strings, and sticks them all together with the empty string as the separating character. If I were to do '+'.join([str(num) for num in alist]), the output would be '2+0+1' instead.

So, the line can be thought of as a series of transformations that slowly converts the initial list into a string.

[2, 0, 1] -> ['2', '0', '1'] -> '201'

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We can also wrap this whole process into a function, like so:

def make_str(list):
    return ''.join([str(num) for num in list])

print make_str([4, 3, 2, 9])  # '4329'
print make_str([9, 0, 0, 9])  # '9009'

Answer 4

What about:

>>> alist = [2, 0, 1]
>>> "".join(str(i) for i in alist)
'201'

The code inside join() method is a generator expression.