Development - Advanced, exercise 33

Text

The algorithm globbing is an algorithm for matching wildcards, which is useful when comparing text strings that may contain wildcard syntax. The most used wildcard is “*” and represent zero or more characters. Examples of use of wildcard search are listed as follows:

• *foo* matches any string containing "foo", e.g. "foo", "fidafoo", "farfoofi", "footer";
• fee* matches any string that begins with "fee", e.g. "fee", "feedoo";
• *fae matches any string that ends with "fae", e.g. "fae", "fafae";
• doe (i.e. no wildcards used) matches exactly with the string "doe".

Write an algorithm in Python – def glob(p, s) – which takes a string p representing the pattern (that may includes zero or more wildcards “*”) and another string s on which searching for the pattern, and returns True if p is matched in s, otherwise it returns False.

Solution

# Test case for the function
def test_glob(p, s, expected):
    result = glob(p, s)
    if result is expected:
        return True
    else:
        return False


# Code of the function
def glob(p, s):
    matches = p.split("*")
    
    for idx, pattern in enumerate(matches):
        if pattern in s:
            pos = s.index(pattern)

            if idx == len(matches) - 1 and pattern == "":
                new_start = len(s)
            elif idx > 0:
                new_start = pos + len(pattern)
            elif pos == 0:
                    new_start = len(pattern)
            else:
                return False

            s = s[new_start:]
        else:
            return False

    return s == ""
            


# Tests
print(test_glob("*foo*", "foo", True))
print(test_glob("*foo*", "fidafoo", True))
print(test_glob("*foo*", "farfoofi", True))
print(test_glob("*foo*", "footer", True))
print(test_glob("*foo*", "fee", False))
print(test_glob("fee*", "fee", True))
print(test_glob("fee*", "feedoo", True))
print(test_glob("fee*", "fooee", False))
print(test_glob("*fae", "fae", True))
print(test_glob("*fae", "fafae", True))
print(test_glob("*fae", "fafaefa", False))
print(test_glob("*fae", "fee", False))
print(test_glob("doe", "doe", True))
print(test_glob("doe", "john doe", False))
print(test_glob("*pa*pe*", "paperino", True))
print(test_glob("*pa*foo*", "paparfoo", True))
print(test_glob("*pa*po*foo*", "papopaporfoo", True))
print(test_glob("*pa*foo*", "paparfoo", True))

Additional material

The runnable Python file is available online.