if re.search(r'pattern', string):

Simple if-regex example:

if re.search(r'ing\b', "seeking a great perhaps"):     # any words end with ing?
    print("yes")

Complex if-regex example (pattern check, extract a substring, case insensitive):

search_object = re.search(r'^OUGHT (.*) BE$', "ought to be", flags=re.IGNORECASE)
if search_object:
    assert "to" == search_object.group(1)     # what's between ought and be?

Notes:

• Use re.search() not re.match. The match method restricts to the start of the string, a confusing convention. If you want that, search explicitly with caret: re.search(r'^...', ...) (Or in re.MULTILINE mode use \A)

• Use raw string syntax r'pattern' for the first parameter. Otherwise you would need to double up backslashes, as in re.search('ing\\b', ...)

• In these examples, '\\b' or r'\b' is a special sequence meaning word-boundary for regex purposes. Not to be confused with '\b' or '\x08' backspace.

• re.search() returns None if it doesn't find anything, which is always falsy.

• re.search() returns a Match object if it finds anything, which is always truthy.

• even though re.search() returns a Match object (type(search_object) is re.Match) I have taken to calling the return value a search_object. I keep returning to my own bloody answer here because I can't remember whether to use match or search. It's search, dammit.

• a group is what matched inside pattern parentheses.

• group numbering starts at 1.

• Specs

• Tutorial