Removing only alpha duplicates

Question

In Python, I would like to remove duplicate letters from a string, but not numbers or spaces. I came up with:

result = []
seen = set()
for char in string:
    if char not in seen:
        seen.add(char)
        result.append(char)
return "".join(result)

But that makes:

>>> delete_duplicate_letters("13 men were wounded in an explosion yesterday around 3:00pm.")
13 menwroudiaxplsyt:0.

When I want:

>>> delete_duplicate_letters("13 men were wounded in an explosion yesterday around 3:00pm.")
13 men wr oud i a xpls yt 3:00.

I've tried to use letter instead of char, the isalpha() function and if int statements etc but I couldn't get anything to work.

Answer 1

Try this:

result = ""
for char in string:
    if not (char.isalpha() and char in result):
        result += char

Answer 2

>>> from string import digits, whitespace
>>> from collections import OrderedDict
>>> s = set(whitespace + digits)
>>> ''.join(OrderedDict((object() if c in s else c, c) for c in text).values())
'12 men wr oud i a xpls yt  3:00.'

object() here is just used to make sure the keys for characters you want to leave are always unique since object() creates a different object each time. The other characters are used as the keys themselves so duplicates are filtered.

Answer 3

use str.isspace and str.isdigit:

strs = "13 men were wounded in an explosion yesterday around 3:00pm."
result = []
seen = set()
for char in strs:
    if char not in seen:
        if not (char.isspace() or char.isdigit()):
           seen.add(char)
        result.append(char)
print "".join(result)

output:

13 men wr oud i a xpls yt  3:00.

Answer 4

Seems like you're almost there. You can just add some checks in the loop:

result = []
seen = set()
for char in string:
    if char.isdigit() or char.isspace():
        result.append(char)
    elif char not in seen:
        seen.add(char)
        result.append(char)
return "".join(result)