String-2.py

def double_char(str):
    """
    Given a string, return a string where for every char in the original, there are two chars.
    """
    return ''.join(c * 2 for c in str)


def count_hi(str):
    """
    Return the number of times that the string "hi" appears anywhere in the given string.
    """
    return str.count('hi')


def cat_dog(str):
    """
    Return True if the string "cat" and "dog" appear the same number of times in the given string.
    """
    return str.count('cat') == str.count('dog')


def count_code(str):
    """
    Return the number of times that the string "code" appears anywhere in the given string,
    except we'll accept any letter for the 'd', so "cope" and "cooe" count.
    """
    return sum(str[i:i + 2] == 'co' and str[i + 3] == 'e' for i in range(len(str) - 3))


def end_other(a, b):
    """
    Given two strings, return True if either of the strings appears at the very end of the other string,
    ignoring upper/lower case differences (in other words, the computation should not be "case sensitive").
    Note: s.lower() returns the lowercase version of a string.
    """
    return a.lower().endswith(b.lower()) or b.lower().endswith(a.lower())


def xyz_there(str):
    """
    Return True if the given string contains an appearance of "xyz" where the xyz is not directly preceeded
    by a period (.). So "xxyz" counts but "x.xyz" does not.
    """
    return str.count('xyz') > str.count('.xyz')