range over character in python

问题:

Is there an way to range over characters? something like this.

for c in xrange( 'a', 'z' ):
    print c

I hope you guys can help.

回答1:

This is a great use for a custom generator:

Python 2:

def char_range(c1, c2):
    """Generates the characters from `c1` to `c2`, inclusive."""
    for c in xrange(ord(c1), ord(c2)+1):
        yield chr(c)

then:

for c in char_range('a', 'z'):
    print c

---

Python 3:

def char_range(c1, c2):
    """Generates the characters from `c1` to `c2`, inclusive."""
    for c in range(ord(c1), ord(c2)+1):
        yield chr(c)

then:

for c in char_range('a', 'z'):
    print(c)

回答2:

import string
for char in string.ascii_lowercase:
    print char

See string constants for the other possibilities, including uppercase, numbers, locale-dependent characters, all of which you can join together like string.ascii_uppercase + string.ascii_lowercase if you want all of the characters in multiple sets.

回答3:

You have to convert the characters to numbers and back again.

for c in xrange(ord('a'), ord('z')+1):
    print chr(c) # resp. print unicode(c)

For the sake of beauty and readability, you can wrap this in a generator:

def character_range(a, b, inclusive=False):
    back = chr
    if isinstance(a,unicode) or isinstance(b,unicode):
        back = unicode
    for c in xrange(ord(a), ord(b) + int(bool(inclusive)))
        yield back(c)

for c in character_range('a', 'z', inclusive=True):
    print(chr(c))

This generator can be called with inclusive=False (default) to imitate Python's usual bhehaviour to exclude the end element, or with inclusive=True (default) to include it. So with the default inclusive=False, 'a', 'z' would just span the range from a to y, excluding z.

If any of a, b are unicode, it returns the result in unicode, otherwise it uses chr.

It currently (probably) only works in Py2.

回答4:

There are other good answers here (personally I'd probably use string.lowercase), but for the sake of completeness, you could use map() and chr() on the lower case ascii values:

for c in map(chr, xrange(97, 123)):
   print c

回答5:

for character in map(   chr, xrange( ord('a'), ord('c')+1 )   ):
   print character

prints:

a
b
c

回答6:

# generating 'a to z' small_chars.
small_chars = [chr(item) for item in range(ord('a'), ord('z')+1)]
# generating 'A to Z' upper chars.
upper_chars = [chr(item).upper() for item in range(ord('a'), ord('z')+1)]

回答7:

If you have a short fixed list of characters, just use Python's treatment of strings as lists.

for x in 'abcd':
    print x

or

[x for x in 'abcd']

回答8:

I like an approach which looks like this:

base64chars = list(chars('AZ', 'az', '09', '++', '//'))

It certainly can be implemented with a lot of more comfort, but it is quick and easy and very readable.

Python 3

Generator version:

def chars(*args):
    for a in args:
        for i in range(ord(a[0]), ord(a[1])+1):
            yield chr(i)

Or, if you like list comprehensions:

def chars(*args):
    return [chr(i) for a in args for i in range(ord(a[0]), ord(a[1])+1)]

The first yields:

print(chars('ĀĈ'))
<generator object chars at 0x7efcb4e72308>
print(list(chars('ĀĈ')))
['Ā', 'ā', 'Ă', 'ă', 'Ą', 'ą', 'Ć', 'ć', 'Ĉ']

while the second yields:

print(chars('ĀĈ'))
['Ā', 'ā', 'Ă', 'ă', 'Ą', 'ą', 'Ć', 'ć', 'Ĉ']

It is really convenient:

base64chars = list(chars('AZ', 'az', '09', '++', '//'))
for a in base64chars:
   print(repr(a),end='')
print('')
for a in base64chars:
   print(repr(a),end=' ')

outputs

'A''B''C''D''E''F''G''H''I''J''K''L''M''N''O''P''Q''R''S''T''U''V''W''X''Y''Z''a''b''c''d''e''f''g''h''i''j''k''l''m''n''o''p''q''r''s''t''u''v''w''x''y''z''0''1''2''3''4''5''6''7''8''9''+''/'
'A' 'B' 'C' 'D' 'E' 'F' 'G' 'H' 'I' 'J' 'K' 'L' 'M' 'N' 'O' 'P' 'Q' 'R' 'S' 'T' 'U' 'V' 'W' 'X' 'Y' 'Z' 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j' 'k' 'l' 'm' 'n' 'o' 'p' 'q' 'r' 's' 't' 'u' 'v' 'w' 'x' 'y' 'z' '0' '1' '2' '3' '4' '5' '6' '7' '8' '9' '+' '/' 

Why the list()? Without base64chars might become a generator (depending on the implementation you chose) and thus can only be used in the very first loop.

Python 2

Similar can be archived with Python 2. But it is far more complex if you want to support Unicode, too. To encourage you to stop using Python 2 in favor of Python 3 I do not bother to provide a Python 2 solution here ;)

Try to avoid Python 2 today for new projects. Also try to port old projects to Python 3 first before extending them - in the long run it will be worth the effort!

Proper handling of Unicode in Python 2 is extremely complex, and it is nearly impossible to add Unicode support to Python 2 projects if this support was not build in from the beginning.

Hints how to backport this to Python 2:

• Use xrange instead of range
• Create a 2nd function (unicodes?) for handling of Unicode:
  • Use unichr instead of chr to return unicode instead of str
  • Never forget to feed unicode strings as args to make ord and array subscript work properly

回答9:

Inspired from the top post above, I came up with this :

map(chr,range(ord('a'),ord('z')+1))                     

回答10:

Use "for count in range" and chr&ord:

print [chr(ord('a')+i) for i in range(ord('z')-ord('a'))]

回答11:

Use list comprehension:

for c in [chr(x) for x in range(ord('a'), ord('z'))]:
    print c

回答12:

Using @ned-batchelder's answer here, I'm amending it a bit for python3

def char_range(c1, c2):
    """Generates the characters from `c1` to `c2`, inclusive."""
    """Using range instead of xrange as xrange is deprecated in Python3""" 
    for c in range(ord(c1), ord(c2)+1):
        yield chr(c)

Then same thing as in Ned's answer:

for c in char_range('a', 'z'):
    print c

Thanks Ned!

回答13:

Another option (operates like range - add 1 to stop if you want stop to be inclusive)

>>> import string
>>> def crange(arg, *args):
...     """character range, crange(stop) or crange(start, stop[, step])"""
...     if len(args):
...         start = string.ascii_letters.index(arg)
...         stop = string.ascii_letters.index(args[0])
...     else:
...         start = string.ascii_letters.index('a')
...         stop = string.ascii_letters.index(arg)
...     step = 1 if len(args) < 2 else args[1]
...     for index in range(start, stop, step):
...         yield string.ascii_letters[index]
...
>>> [_ for _ in crange('d')]
['a', 'b', 'c']
>>>
>>> [_ for _ in crange('d', 'g')]
['d', 'e', 'f']
>>>
>>> [_ for _ in crange('d', 'v', 3)]
['d', 'g', 'j', 'm', 'p', 's']
>>>
>>> [_ for _ in crange('A', 'G')]
['A', 'B', 'C', 'D', 'E', 'F']