如果我没有理解错您的需求，您需要以下模式：

^[A-Z]{3,4}[0-9]{4}$

这里假设你要在多行模式下使用正则表达式搜索存储在Python字符串中的整个文本，参见这个演示：

inp = """MAT1051
CMP1401*
PHY1001*
MAT1041*
ENG1003*"""

matches = re.findall(r'^[A-Z]{3,4}[0-9]{4}$', inp, flags=re.M)
print(matches)  # ['MAT1051']

import re
# Add a "$" at the end of the re.
# It requires the match to end after the 4 digits.
course_code = re.compile('[A-Z]{4}[0-9]{4}$|[A-Z]{3}[0-9]{4}$')

# No match here
m = re.match(course_code, "MAT1051*")
print(m)
# This matches
m = re.match(course_code, "MAT1051")
print(m)