Most characters match themselves. A few are special:

Pattern	Matches
`.`	any character except a new line
`\d`	a digit
`\w`	a "word" character: letter, digit or underscore
`\s`	whitespace: space, tab, new line
`\D`, `\W`, `\S`	anything that isn't a digit, word character, whitespace
`[aeiou]`	any one of these characters
`[a-z]`	any character in this range
`[^0-9]`	any character not in the set
`^`	the start of the text
`$`	the end of the text
`\b`	a word boundary (the edge of a word)

To match a special character literally, put a backslash before it: \. matches a full stop, \$ a dollar sign.

import re

print(re.findall(r"[A-Z]\w*", "Ada met Grace and Alan in London"))
print(re.findall(r"\bcat\b", "cat concatenate cat."))
print(bool(re.search(r"^\d", "7 dwarves")), bool(re.search(r"^\d", "Seven dwarves")))