satisfiesF.py

def satisfiesF(L):
    """
    Assumes L is a list of strings
    Assume function f is already defined for you and it maps a string to a Boolean
    Mutates L such that it contains all of the strings, s, originally in L such
            that f(s) returns True, and no other elements. Remaining elements in L
            should be in the same order.
    Returns the length of L after mutation
    """
    # Your function implementation here

    L_delete = []
    for string in L:
        if f(string)==False:
            L_delete.append(string)
    
    for string in L_delete:
        L.remove(string)
        
    return len(L)

run_satisfiesF(L, satisfiesF)

def f(s):
    return 'a' in s
      
L = ['a', 'b', 'a']
print satisfiesF(L)
print L