String representation of arrays in python

Question

Is there anything that performs the following, in python? Or will I have to implement it myself?

array = [0, 1, 2]
myString = SOME_FUNCTION_THAT_TAKES_AN_ARRAY_AS_INPUT(array)
print myString

which prints

(0, 1, 2)

Thanks

'print array' works... are you specifically interested in the parentheses? — EMiller
– EMiller, Commented Dec 13, 2009 at 4:30
You should know and use the various names of the sequence types, which are [list], (tuple,..) and {'dict':..}. They all have different behaviour. What you want is to convert a list to a tuple, and that can be done just by print tuple(list). See also Prasoon's answer, which is correct. — Tor Valamo
– Tor Valamo, Commented Dec 13, 2009 at 6:28
I think everyone has taken the question too literally, and what devoured elysium is looking for is just str(array). — Jason Orendorff
– Jason Orendorff, Commented Dec 13, 2009 at 7:01

Dan Loewenherz · Accepted Answer · 2009-12-13 04:28:36Z

5

You're in luck, Python has a function for this purpose exactly. It's called join.

print "(" + ", ".join(array) + ")"

If you're familiar with PHP, join is similar to implode. The ", " above is the element separator, and can be replaced with any string. For example,

print "123".join(['a','b','c'])

will print

a123b123c

answered Dec 13, 2009 at 4:28

Dan Loewenherz

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1 Comment

jakecard Over a year ago

This will work in your example, but not in the one the submitter gave, since he used ints. You could use ", ".join([str(x) for x in array]) though.

jakecard · Accepted Answer · 2009-12-13 04:55:39Z

5

def SOME_FUNCTION_THAT_TAKES_AN_ARRAY_AS_INPUT (arr):
    return str(tuple(arr))

Replace str with unicode if you need to.

answered Dec 13, 2009 at 4:55

jakecard

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Comments

Alok Singhal · Accepted Answer · 2009-12-13 04:29:25Z

4

SOME_FUNCTION_THAT_TAKES_AN_ARRAY_AS_INPUT = tuple

answered Dec 13, 2009 at 4:29

Alok Singhal

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2 Comments

Alex Martelli Over a year ago

The OP claims he wants a string (though his use of print obfuscates that;-).

Alok Singhal Over a year ago

I know. My comment was more of a tongue-in-cheek remark, particularly because I got a kick out of his use of "SOME_FUNCTION_THAT_TAKES_AN_ARRAY_AS_INPUT". :-)

Alex Martelli · Accepted Answer · 2009-12-13 06:04:50Z

If your array's items are specifically integers, str(tuple(array)) as suggested in @jboxer's answer will work. For most other types of items, it may be more of a problem, since str(tuple(...)) uses repr, not str -- that's really needed as a default behavior (otherwise printing a tuple with an item such as the string '1, 2' would be extremely confusing, looking just like a string with the two int items 1 and 2!-), but it may or may not be what you want. For example:

>>> array = [0.1, 0.2]
>>> print str(tuple(array))
(0.10000000000000001, 0.20000000000000001)

With floating point numbers, repr emits many more digits than make sense in most cases (while str, if called directly on the numbers, behaves a bit better). So if your items are liable to be floats (as well as ints, which would need no precaution but won't be hurt by this one;-), you might better off with:

>>> print '(%s)' % (', '.join(str(x) for x in array))
(0.1, 0.2)

However, this might produce ambiguous output if some of the items are strings, as I mentioned earlier!

If you know what types of data you're liable to have in the list which you call "array", it would give a better basis on which to recommend a solution.

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