def remove_all(a, b):
    while True:
        f = b.find(a)
        if f == -1:
            break
        b = b[:f] + b[f + len(a):]
    return b


print(remove_all('an', 'banana'))
print(remove_all('cyc', 'bicycle'))
print(remove_all('iss', 'Mississippi'))
print(remove_all('eggs', 'bicycle'))