Need to sort given strings (Strings starting with x first)

Question

Code doesn't return last word when given ['mix', 'xyz', 'apple', 'xanadu', 'aardvark'] list.

def front_x(words):
    x_list = []
    no_x_list = []
    [x_list.append(i) for i in words if i[0] == "x"]
    [no_x_list.append(words[i2]) for i2 in range(len(words)-1) if words[i2] not in x_list]
    x_list.sort()
    no_x_list.sort()
    return x_list + no_x_list
print front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark'])

Must be:

['xanadu', 'xyz', 'aardvark', 'apple', 'mix']

With lists ['bbb', 'ccc', 'axx', 'xzz', 'xaa'] and ['ccc', 'bbb', 'aaa', 'xcc', 'xaa'] everything is right ['xaa', 'xzz', 'axx', 'bbb', 'ccc'] and ['xaa', 'xcc', 'aaa', 'bbb', 'ccc']

Answer 1

Iterating on range(len(words)-1) looks incorrect. More so, making list appends with list comprehension is quite unpythonic; list comps are for building lists not making making list appends which is rather ironic here.

You can perform the sort once by sorting based on a two-tuple whose fist item checks if a word startswith 'x' and puts those ahead. The second item in the tuple applies a lexicograhical sort on the list, breaking ties:

def front_x(words):
    return sorted(words, key=lambda y: (not y.startswith('x'), y))

print front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark'])
# ['xanadu', 'xyz', 'aardvark', 'apple', 'mix']

Answer 2

Just remove the -1 from range(len(words)-1) This will be the minimal change in your code.

Answer 3

You can try this:

words = ['mix', 'xyz', 'apple', 'xanadu', 'aardvark']

new_words = [i for i in words if i[0].lower() == "x"]

words = [i for i in words if i[0].lower() != "x"]

final_words = sorted(new_words)+sorted(words)

print(final_words)

Output:

['xanadu', 'xyz', 'aardvark', 'apple', 'mix']

Answer 4

You have to use len(words) instead of len(words)-1 to get expected output.

So, try this way :

def front_x(words):
    x_list = []
    no_x_list = []
    [x_list.append(i) for i in words if i[0] == "x"]
    [no_x_list.append(words[i2]) for i2 in range(len(words)) if words[i2] not in x_list]
    x_list.sort()
    no_x_list.sort()
    return x_list + no_x_list

print front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark'])

Output :

['xanadu', 'xyz', 'aardvark', 'apple', 'mix']