I want to replace dashes which appear between letters with a space using regex. For example to replace ab-cd with ab cd
The following matches the character-character sequence, however also replaces the characters [i.e. ab-cd results in a d, rather than ab cd as i desire]
new_term = re.sub(r"[A-z]\-[A-z]", " ", original_term)
How i adapt the above to only replace the - part?
You need to capture the characters before and after the - to a group and use them for replacement, i.e.:
import re
subject = "ab-cd"
subject = re.sub(r"([a-z])\-([a-z])", r"\1 \2", subject , 0, re.IGNORECASE)
print subject
#ab cd
DEMO
REGEX EXPLANATION
([A-z])\-([A-z])
Match the regex below and capture its match into backreference number 1 «([A-z])»
Match a single character in the range between “A” and “z” «[A-z]»
Match the character “-” literally «\-»
Match the regex below and capture its match into backreference number 2 «([A-z])»
Match a single character in the range between “A” and “z” «[A-z]»
\1 \2
Insert the text that was last matched by capturing group number 1 «\1»
Insert the character “ ” literally « »
Insert the text that was last matched by capturing group number 2 «\2»
Use references to capturing groups:
>>> original_term = 'ab-cd'
>>> re.sub(r"([A-z])\-([A-z])", r"\1 \2", original_term)
'ab cd'
This assumes, of course, that you can't just do original_term.replace('-', ' ') for whatever reason. Perhaps your text uses hyphens where it should use en dashes or something.
[A-z] since regex ranges uses ascii table index. For this specific range you will match A-Z[\]^_`a-z. However, you can use (?i) if you want to use a-z as key insensitive. For instance, you can have (?i)([a-z])\-([a-z]). Anyway, I know OP original regex is that... but just saying.re.sub() always replaces the whole matched sequence with the replacement.
A solution to only replace the dash are lookahead and lookbehind assertions. They don't count to the matched sequence.
new_term = re.sub(r"(?<=[A-z])\-(?=[A-z])", " ", original_term)
The syntax is explained in the Python documentation for the re module.
You need to use look-arounds:
new_term = re.sub(r"(?<=[A-Za-z])-(?=[A-Za-z])", " ", original_term)
Or capturing groups:
new_term = re.sub(r"([A-Za-z])-(?=[A-Za-z])", r"\1 ", original_term)
See IDEONE demo
Note that [A-z] also matches some non-letters (namely [, \, ], ^, _, and `), thus, I suggest replacing it with [A-Z] and use a case-insensitive modifier (?i).
Note that you do not have to escape a hyphen outside a character class.
I think there's a simple way to replace dashes using Visual Basic, in a multiline textbox:
Regex.Replace(ReadText.Text, "[-]", " ")
-with a space in the given string? Is using regex necessary?ab-cd, but not to changeab - cd- [replacedoesn't have that control].