匹配字符串开头，中间和结尾的完整单词

Question

How to replace the complete word abc.def at start, middle and end of string but do not replace the text like abc.def.au or d.abc.def :

line = "abc.def abc.def.au abc.def d.abc.def abc.def"
new_line = re.sub("abc.def", "-----", line)
print(line)
print(new_line)

Current output:

abc.def abc.def.au abc.def d.abc.def abc.def
----- -----.au ----- d.----- -----

Expected output:

abc.def abc.def.au abc.def d.abc.def abc.def
----- abc.def.au ----- d.abc.def -----

Can this be done in one re.sub() ?

Answer 1

You can use line anchors. ^ and $ matches only a the start of the string and end of the string respectively, so you could use them like such:

line = "abc.def abc.def.au abc.def d.abc.def abc.def"
new_line = re.sub(r"^abc\.def|abc\.def$", "-----", line)
print(line)
print(new_line)

Note that it is safer to raw regex strings, and escape the . character (which matches almost any character in regex).

---

If you want to replace only whole words you will need some lookarounds instead:

line = "abc.def abc.def.au abc.def d.abc.def abc.def"
new_line = re.sub(r"(?<!\S)abc\.def(?!\S)", "-----", line)
print(line)
print(new_line)

ideone demo

(?<!\\S) will prevent a match if abc.def is preceded by a non-space character.

(?!\\S) will prevent a match if abc.def is followed by a non-space character.