How can I split a string into substrings based on the characters contained in the substrings. For example, given a string "ABC12345..::", I would like to get a list like ['ABC', '12345', '..::']. I know the valid characters for each substring, but I don't know the lengths. So the string could also look like "CC123:....:", in which case I would like to have ['CC', '123', ':....:'] as the result.
By your example you don't seem to have anything to split with (e.g. nothing between C and 1), but what you do have is a well-formed pattern that you can match. So just simply create a pattern that groups the strings you want matched:
>>> import re
>>> s = "ABC12345..::"
>>> re.match('([A-Z]*)([0-9]*)([\.:]*)', s).groups()
('ABC', '12345', '..::')
Alternative, compile the pattern into a reusable regex object and do this:
>>> patt = re.compile('([A-Z]*)([0-9]*)([\.:]*)')
>>> patt.match(s).groups()
('ABC', '12345', '..::')
>>> patt.match("CC123:....:").groups()
('CC', '123', ':....:')
Match each group with the following regex
[0-9]+|[a-zA-Z]+|[.:]+
[0-9]+ any digits repeated any times, or
[a-zA-Z]+ any letters repeated any times, or
[.:]+ any dots or colons repeated any times
This will allow you to match groups in any order, ie: "123...xy::ab..98765PQRS".
import re
print(re.findall( r'[0-9]+|[a-zA-Z]+|[.:]+', "ABC12345..::"))
# => ['ABC', '12345', '..::']
ideone demo
If you want a non-regex approach:
value = 'ABC12345..::'
indexes = [i for i, char in enumerate(value) if char.isdigit()] # Collect indexes of any digits
arr = [ value[:indexes[0]], value[indexes[0]:indexes[-1]+1], value[indexes[-1]+1:] ] # Use splicing to build list
Output:
['ABC', '12345', '..::']
Another string:
value = "CC123:....:"
indexes = [i for i, char in enumerate(value) if char.isdigit()] # Collect indexes of any digits
arr = [ value[:indexes[0]], value[indexes[0]:indexes[-1]+1], value[indexes[-1]+1:] ] # Use splicing to build list
Output:
['CC', '123', ':....:']
EDIT:
Just did a benchmark, metatoaster's method is slightly faster than this :)
so i'm trying to make a program in Python PyScripter 3.3 that takes input, and converts the input into an acronym. This is what i'm looking for.
your input: center of earth
programs output: C.O.E.
I don't really know how to go about doing this, I am looking for not just the right answer, but an explanation of why certain code is used, thanks..
What I have tried so far:
def first_letters(lst):
return [s[:1] for s in converted]
def main():
lst = input("What is the phrase you wish to convert into an acronym?")
converted = lst.split().upper()
Beyond here I am not really sure where to go, so far I know I need to captialize the input, split it into separate words, and then beyond that im not sure where to go...
I like Python 3.
>>> s = 'center of earth'
>>> print(*(word[0] for word in s.upper().split()), sep='.', end='.\n')
C.O.E.
s = 'center of earth' - Assign the string.
s.upper() - Make the string uppercase. This goes before split() because split() returns a list and upper() doesn't work on lists.
.split() - Split the uppercased string into a list.
for word in - Iterate through each element of the created list.
word[0] - The first letter of each word.
* - Unpack this generator and pass each element as an argument to the print function.
sep='.' - Specify a period to separate each printed argument.
end='.\n' - Specify a period and a newline to print after all the arguments.
print - Print it.
As an alternative:
>>> s = 'center of earth'
>>> '.'.join(filter(lambda x: x.isupper(), s.title())) + '.'
'C.O.E.'
s = 'center of earth' - Assign the string.
s.title() - Change the string to Title Case.
filter - Filter the string, retaining only those elements that are approved by a predicate (the lambda below).
lambda x: x.isupper() - Define an anonymous inline function that takes an argument x and returns whether x is uppercase.
'.'.join - Join all the filtered elements with a '.'.
+ '.' - Add a period to the end.
Note that this one returns a string instead of simply printing it to the console.
>>> import re
>>> s = "center of earth"
>>> re.sub('[a-z ]+', '.', s.title())
'C.O.E.'
>>> "".join(i[0].upper() + "." for i in s.split())
'C.O.E.'
Since you want an explanation and not just an answer:
>>> s = 'center of earth'
>>> s = s.split() # split it into words
>>> s
['center', 'of', 'earth']
>>> s = [i[0] for i in s] # get only the first letter or each word
>>> s
['c', 'o', 'e']
>>> s = [i.upper() for i in s] # convert the letters to uppercase
>>> s
['C', 'O', 'E']
>>> s = '.'.join(s) # join the letters into a string
>>> s
'C.O.E'
>>> s = s + '.' # add the dot at the end
>>> s
'C.O.E.'
What I was trying to achieve, was something like this:
>>> camel_case_split("CamelCaseXYZ")
['Camel', 'Case', 'XYZ']
>>> camel_case_split("XYZCamelCase")
['XYZ', 'Camel', 'Case']
So I searched and found this perfect regular expression:
(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])
As the next logical step I tried:
>>> re.split("(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])", "CamelCaseXYZ")
['CamelCaseXYZ']
Why does this not work, and how do I achieve the result from the linked question in python?
Edit: Solution summary
I tested all provided solutions with a few test cases:
string: ''
AplusKminus: ['']
casimir_et_hippolyte: []
two_hundred_success: []
kalefranz: string index out of range # with modification: either [] or ['']
string: ' '
AplusKminus: [' ']
casimir_et_hippolyte: []
two_hundred_success: [' ']
kalefranz: [' ']
string: 'lower'
all algorithms: ['lower']
string: 'UPPER'
all algorithms: ['UPPER']
string: 'Initial'
all algorithms: ['Initial']
string: 'dromedaryCase'
AplusKminus: ['dromedary', 'Case']
casimir_et_hippolyte: ['dromedary', 'Case']
two_hundred_success: ['dromedary', 'Case']
kalefranz: ['Dromedary', 'Case'] # with modification: ['dromedary', 'Case']
string: 'CamelCase'
all algorithms: ['Camel', 'Case']
string: 'ABCWordDEF'
AplusKminus: ['ABC', 'Word', 'DEF']
casimir_et_hippolyte: ['ABC', 'Word', 'DEF']
two_hundred_success: ['ABC', 'Word', 'DEF']
kalefranz: ['ABCWord', 'DEF']
In summary you could say the solution by #kalefranz does not match the question (see the last case) and the solution by #casimir et hippolyte eats a single space, and thereby violates the idea that a split should not change the individual parts. The only difference among the remaining two alternatives is that my solution returns a list with the empty string on an empty string input and the solution by #200_success returns an empty list.
I don't know how the python community stands on that issue, so I say: I am fine with either one. And since 200_success's solution is simpler, I accepted it as the correct answer.
As #AplusKminus has explained, re.split() never splits on an empty pattern match. Therefore, instead of splitting, you should try finding the components you are interested in.
Here is a solution using re.finditer() that emulates splitting:
def camel_case_split(identifier):
matches = finditer('.+?(?:(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])|$)', identifier)
return [m.group(0) for m in matches]
Use re.sub() and split()
import re
name = 'CamelCaseTest123'
splitted = re.sub('([A-Z][a-z]+)', r' \1', re.sub('([A-Z]+)', r' \1', name)).split()
Result
'CamelCaseTest123' -> ['Camel', 'Case', 'Test123']
'CamelCaseXYZ' -> ['Camel', 'Case', 'XYZ']
'XYZCamelCase' -> ['XYZ', 'Camel', 'Case']
'XYZ' -> ['XYZ']
'IPAddress' -> ['IP', 'Address']
Most of the time when you don't need to check the format of a string, a global research is more simple than a split (for the same result):
re.findall(r'[A-Z](?:[a-z]+|[A-Z]*(?=[A-Z]|$))', 'CamelCaseXYZ')
returns
['Camel', 'Case', 'XYZ']
To deal with dromedary too, you can use:
re.findall(r'[A-Z]?[a-z]+|[A-Z]+(?=[A-Z]|$)', 'camelCaseXYZ')
Note: (?=[A-Z]|$) can be shorten using a double negation (a negative lookahead with a negated character class): (?![^A-Z])
Working solution, without regexp
I am not that good at regexp. I like to use them for search/replace in my IDE but I try to avoid them in programs.
Here is a quite straightforward solution in pure python:
def camel_case_split(s):
idx = list(map(str.isupper, s))
# mark change of case
l = [0]
for (i, (x, y)) in enumerate(zip(idx, idx[1:])):
if x and not y: # "Ul"
l.append(i)
elif not x and y: # "lU"
l.append(i+1)
l.append(len(s))
# for "lUl", index of "U" will pop twice, have to filter that
return [s[x:y] for x, y in zip(l, l[1:]) if x < y]
And some tests
TESTS = [
("XYZCamelCase", ['XYZ', 'Camel', 'Case']),
("CamelCaseXYZ", ['Camel', 'Case', 'XYZ']),
("CamelCaseXYZa", ['Camel', 'Case', 'XY', 'Za']),
("XYZCamelCaseXYZ", ['XYZ', 'Camel', 'Case', 'XYZ']),
("aCamelCaseWordT", ['a', 'Camel', 'Case', 'Word', 'T']),
("CamelCaseWordT", ['Camel', 'Case', 'Word', 'T']),
("CamelCaseWordTa", ['Camel', 'Case', 'Word', 'Ta']),
("aCamelCaseWordTa", ['a', 'Camel', 'Case', 'Word', 'Ta']),
("Ta", ['Ta']),
("aT", ['a', 'T']),
("a", ['a']),
("T", ['T']),
("", []),
]
def test():
for (q,a) in TESTS:
assert camel_case_split(q) == a
if __name__ == "__main__":
test()
Edit: a solution which streams data in one pass
This solution leverages the fact that the decision to split word or not can be taken locally, just considering the current character and the previous one.
def camel_case_split(s):
u = True # case of previous char
w = b = '' # current word, buffer for last uppercase letter
for c in s:
o = c.isupper()
if u and o:
w += b
b = c
elif u and not o:
if len(w)>0:
yield w
w = b + c
b = ''
elif not u and o:
yield w
w = ''
b = c
else: # not u and not o:
w += c
u = o
if len(w)>0 or len(b)>0: # flush
yield w + b
It is theoretically faster and lesser memory usage.
same tests suite applies
but list must be built by caller
def test():
for (q,a) in TESTS:
r = list(camel_case_split(q))
print(q,a,r)
assert r == a
Try it online
I just stumbled upon this case and wrote a regular expression to solve it. It should work for any group of words, actually.
RE_WORDS = re.compile(r'''
# Find words in a string. Order matters!
[A-Z]+(?=[A-Z][a-z]) | # All upper case before a capitalized word
[A-Z]?[a-z]+ | # Capitalized words / all lower case
[A-Z]+ | # All upper case
\d+ # Numbers
''', re.VERBOSE)
The key here is the lookahead on the first possible case. It will match (and preserve) uppercase words before capitalized ones:
assert RE_WORDS.findall('FOOBar') == ['FOO', 'Bar']
import re
re.split('(?<=[a-z])(?=[A-Z])', 'camelCamelCAMEL')
# ['camel', 'Camel', 'CAMEL'] <-- result
# '(?<=[a-z])' --> means preceding lowercase char (group A)
# '(?=[A-Z])' --> means following UPPERCASE char (group B)
# '(group A)(group B)' --> 'aA' or 'aB' or 'bA' and so on
The documentation for python's re.split says:
Note that split will never split a string on an empty pattern match.
When seeing this:
>>> re.findall("(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])", "CamelCaseXYZ")
['', '']
it becomes clear, why the split does not work as expected. The remodule finds empty matches, just as intended by the regular expression.
Since the documentation states that this is not a bug, but rather intended behavior, you have to work around that when trying to create a camel case split:
def camel_case_split(identifier):
matches = finditer('(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])', identifier)
split_string = []
# index of beginning of slice
previous = 0
for match in matches:
# get slice
split_string.append(identifier[previous:match.start()])
# advance index
previous = match.start()
# get remaining string
split_string.append(identifier[previous:])
return split_string
This solution also supports numbers, spaces, and auto remove underscores:
def camel_terms(value):
return re.findall('[A-Z][a-z]+|[0-9A-Z]+(?=[A-Z][a-z])|[0-9A-Z]{2,}|[a-z0-9]{2,}|[a-zA-Z0-9]', value)
Some tests:
tests = [
"XYZCamelCase",
"CamelCaseXYZ",
"Camel_CaseXYZ",
"3DCamelCase",
"Camel5Case",
"Camel5Case5D",
"Camel Case XYZ"
]
for test in tests:
print(test, "=>", camel_terms(test))
results:
XYZCamelCase => ['XYZ', 'Camel', 'Case']
CamelCaseXYZ => ['Camel', 'Case', 'XYZ']
Camel_CaseXYZ => ['Camel', 'Case', 'XYZ']
3DCamelCase => ['3D', 'Camel', 'Case']
Camel5Case => ['Camel', '5', 'Case']
Camel5Case5D => ['Camel', '5', 'Case', '5D']
Camel Case XYZ => ['Camel', 'Case', 'XYZ']
Simple solution:
re.sub(r"([a-z0-9])([A-Z])", r"\1 \2", str(text))
Here's another solution that requires less code and no complicated regular expressions:
def camel_case_split(string):
bldrs = [[string[0].upper()]]
for c in string[1:]:
if bldrs[-1][-1].islower() and c.isupper():
bldrs.append([c])
else:
bldrs[-1].append(c)
return [''.join(bldr) for bldr in bldrs]
Edit
The above code contains an optimization that avoids rebuilding the entire string with every appended character. Leaving out that optimization, a simpler version (with comments) might look like
def camel_case_split2(string):
# set the logic for creating a "break"
def is_transition(c1, c2):
return c1.islower() and c2.isupper()
# start the builder list with the first character
# enforce upper case
bldr = [string[0].upper()]
for c in string[1:]:
# get the last character in the last element in the builder
# note that strings can be addressed just like lists
previous_character = bldr[-1][-1]
if is_transition(previous_character, c):
# start a new element in the list
bldr.append(c)
else:
# append the character to the last string
bldr[-1] += c
return bldr
I know that the question added the tag of regex. But still, I always try to stay as far away from regex as possible. So, here is my solution without regex:
def split_camel(text, char):
if len(text) <= 1: # To avoid adding a wrong space in the beginning
return text+char
if char.isupper() and text[-1].islower(): # Regular Camel case
return text + " " + char
elif text[-1].isupper() and char.islower() and text[-2] != " ": # Detect Camel case in case of abbreviations
return text[:-1] + " " + text[-1] + char
else: # Do nothing part
return text + char
text = "PathURLFinder"
text = reduce(split_camel, a, "")
print text
# prints "Path URL Finder"
print text.split(" ")
# prints "['Path', 'URL', 'Finder']"
EDIT:
As suggested, here is the code to put the functionality in a single function.
def split_camel(text):
def splitter(text, char):
if len(text) <= 1: # To avoid adding a wrong space in the beginning
return text+char
if char.isupper() and text[-1].islower(): # Regular Camel case
return text + " " + char
elif text[-1].isupper() and char.islower() and text[-2] != " ": # Detect Camel case in case of abbreviations
return text[:-1] + " " + text[-1] + char
else: # Do nothing part
return text + char
converted_text = reduce(splitter, text, "")
return converted_text.split(" ")
split_camel("PathURLFinder")
# prints ['Path', 'URL', 'Finder']
Putting a more comprehensive approach otu ther. It takes care of several issues like numbers, string starting with lower case, single letter words etc.
def camel_case_split(identifier, remove_single_letter_words=False):
"""Parses CamelCase and Snake naming"""
concat_words = re.split('[^a-zA-Z]+', identifier)
def camel_case_split(string):
bldrs = [[string[0].upper()]]
string = string[1:]
for idx, c in enumerate(string):
if bldrs[-1][-1].islower() and c.isupper():
bldrs.append([c])
elif c.isupper() and (idx+1) < len(string) and string[idx+1].islower():
bldrs.append([c])
else:
bldrs[-1].append(c)
words = [''.join(bldr) for bldr in bldrs]
words = [word.lower() for word in words]
return words
words = []
for word in concat_words:
if len(word) > 0:
words.extend(camel_case_split(word))
if remove_single_letter_words:
subset_words = []
for word in words:
if len(word) > 1:
subset_words.append(word)
if len(subset_words) > 0:
words = subset_words
return words
My requirement was a bit more specific than the OP. In particular, in addition to handling all OP cases, I needed the following which the other solutions do not provide:
- treat all non-alphanumeric input (e.g. !##$%^&*() etc) as a word separator
- handle digits as follows:
- cannot be in the middle of a word
- cannot be at the beginning of the word unless the phrase starts with a digit
def splitWords(s):
new_s = re.sub(r'[^a-zA-Z0-9]', ' ', # not alphanumeric
re.sub(r'([0-9]+)([^0-9])', '\\1 \\2', # digit followed by non-digit
re.sub(r'([a-z])([A-Z])','\\1 \\2', # lower case followed by upper case
re.sub(r'([A-Z])([A-Z][a-z])', '\\1 \\2', # upper case followed by upper case followed by lower case
s
)
)
)
)
return [x for x in new_s.split(' ') if x]
Output:
for test in ['', ' ', 'lower', 'UPPER', 'Initial', 'dromedaryCase', 'CamelCase', 'ABCWordDEF', 'CamelCaseXYZand123.how23^ar23e you doing AndABC123XYZdf']:
print test + ':' + str(splitWords(test))
:[]
:[]
lower:['lower']
UPPER:['UPPER']
Initial:['Initial']
dromedaryCase:['dromedary', 'Case']
CamelCase:['Camel', 'Case']
ABCWordDEF:['ABC', 'Word', 'DEF']
CamelCaseXYZand123.how23^ar23e you doing AndABC123XYZdf:['Camel', 'Case', 'XY', 'Zand123', 'how23', 'ar23', 'e', 'you', 'doing', 'And', 'ABC123', 'XY', 'Zdf']
Maybe this will be enough to for some people:
a = "SomeCamelTextUpper"
def camelText(val):
return ''.join([' ' + i if i.isupper() else i for i in val]).strip()
print(camelText(a))
It dosen't work with the type "CamelXYZ", but with 'typical' CamelCase scenario should work just fine.
I think below is the optimim
Def count_word():
Return(re.findall(‘[A-Z]?[a-z]+’, input(‘please enter your string’))
Print(count_word())
Is there a better way to pull A and F from this: A13:F20
a="A13:F20"
import re
pattern = re.compile(r'\D+\d+\D+')
matches = re.search(pattern, a)
num = matches.group(0)
print num[0]
print num[len(num)-1]
output
A
F
note: the digits are of unknown length
You don't have to use regular expressions, or re at all. Assuming you want just letters to remain, you could do something like this:
a = "A13:F20"
a = filter(lambda x: x.isalpha(), a)
I'd do it like this:
>>> re.findall(r'[a-z]', a, re.IGNORECASE)
['A', 'F']
Use a simple list comprehension, as a filter and get only the alphabets from the actual string.
print [char for char in input_string if char.isalpha()]
# ['A', 'F']
You could use re.sub:
>>> a="A13.F20"
>>> re.sub(r'[^A-Z]', '', a) # Remove everything apart from A-Z
'AF'
>>> re.sub(r'[A-Z]', '', a) # Remove A-Z
'13.20'
>>>
If you're working with strings that all have the same format, you can just cut out substrings:
a="A13:F20"
print a[0], a[4]
More on python slicing in this answer:
Is there a way to substring a string in Python?
Say, if I have a text like
text='a!a b! c!!!'
I want an outcome like this:
text='a!a b c'
So, if the end of each words is '!', I want to get rid of it. If there are multiple '!' in the end of a word, all of them will be eliminated.
print " ".join(word.rstrip("!") for word in text.split())
As an alternative to the split/strip approach
" ".join(x.rstrip("!") for x in text.split())
which won't preserve whitespace exactly, you could perhaps use a regex such as
re.sub(r"!+\B", "", text)
which blanks out all exclamations that aren't immediate followed by the start of a word.
import re
>>> testWord = 'a!a b! c!!!'
>>> re.sub(r'(!+)(?=\s|$)', '', testWord)
'a!a b c'
This preserves any extra spaces you may have in your string which does not happen with str.split()
Here's a non-regex, non-split based approach:
from itertools import groupby
def word_rstrip(s, to_rstrip):
words = (''.join(g) for k,g in groupby(s, str.isspace))
new_words = (w.rstrip(to_strip) for w in words)
return ''.join(new_words)
This works first by using itertools.groupby to group together contiguous characters based on whether or not they're whitespace:
>>> s = "a!a b! c!!"
>>> [''.join(g) for k,g in groupby(s, str.isspace)]
['a!a', ' ', 'b!', ' ', 'c!!']
Effectively, this is like a whitespace-preserving .split(). Once we've got this, we can use rstrip as we always would, and then recombine:
>>> [''.join(g).rstrip("!") for k,g in groupby(s, str.isspace)]
['a!a', ' ', 'b', ' ', 'c']
>>> ''.join(''.join(g).rstrip("!") for k,g in groupby(s, str.isspace))
'a!a b c'
We can also pass whatever we like:
>>> word_rstrip("a!! this_apostrophe_won't_vanish these_ones_will'''", "!'")
"a this_apostrophe_won't_vanish these_ones_will"