Anchors

• \A

• \Z

• ^

• $

• \A matches the beginning of the string

• \Z matches the end of the string

• ^ matches the beginning of the row (see also re.MULTILINE)

• $ matches the end of the row but will accept a trailing newline (see also re.MULTILINE)

import re

lines = [
    "text with cat in the middle",
    "cat with dog",
    "dog with cat",
]

for line in lines:
    if re.search(r'cat', line):
        print(line)


print("---")
for line in lines:
    if re.search(r'^cat', line):
        print(line)

print("---")
for line in lines:
    if re.search(r'\Acat', line):
        print(line)

print("---")
for line in lines:
    if re.search(r'cat$', line):
        print(line)

print("---")
for line in lines:
    if re.search(r'cat\Z', line):
        print(line)

Output:

text with cat in the middle
cat with dog
dog with cat
---
cat with dog
---
cat with dog
---
dog with cat
---
dog with cat