Adding values from for-loop into an array

Question

I'm trying to get the length of the values of the states array into a separate array then sort them by descending order, but I'm having trouble getting all the length values of the string into the array instead of having a single value after the iteration.

states = ["Abia", "Adamawa", "Anambra", "Akwa Ibom", "Bauchi", "Bayelsa", "Benue", "Borno", "Cross River", "Delta", "Ebonyi", "Enugu", "Edo", "Ekiti", "Gombe", "Imo", "Jigawa", "Kaduna", "Kano", "Katsina", "Kebbi", "Kogi", "Kwara", "Lagos", "Nasarawa", "Niger", "Ogun", "Ondo", "Osun", "Oyo", "Plateau", "Rivers", "Sokoto", "Taraba", "Yobe", "Zamfara"]

for i in states:
    a = [len(i)]
    print(a)

Sheldore · Accepted Answer · 2018-08-21 09:37:44Z

3

Since you want the lengths sorted in descending order, use sorted with reverse=True and list comprehension

states = ["Abia", "Adamawa", "Anambra", "Akwa Ibom", "Bauchi", "Bayelsa", "Benue", "Borno", "Cross River", "Delta", "Ebonyi", "Enugu", "Edo", "Ekiti", "Gombe", "Imo", "Jigawa", "Kaduna", "Kano", "Katsina", "Kebbi", "Kogi", "Kwara", "Lagos", "Nasarawa", "Niger", "Ogun", "Ondo", "Osun", "Oyo", "Plateau", "Rivers", "Sokoto", "Taraba", "Yobe", "Zamfara"]
a = sorted([len(i) for i in states], reverse=True)
print (a)

Output

[11, 9, 8, 7, 7, 7, 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3]

To get the indices of the sorted list without resorting to NumPy arrays, there are many ways: see here. I personally prefer to directly make use of NumPy's argsort. As the name suggests, it returns an array of indices corresponding to the sorted array/list in ascending order. To get the indices for descending order, you can just reverse the array returned by argsort by using [::-1]. Following is a solution to your problem:

import numpy as np
states = ["Abia", "Adamawa", "Anambra", "Akwa Ibom", "Bauchi", "Bayelsa", "Benue", "Borno", "Cross River", "Delta", "Ebonyi", "Enugu", "Edo", "Ekiti", "Gombe", "Imo", "Jigawa", "Kaduna", "Kano", "Katsina", "Kebbi", "Kogi", "Kwara", "Lagos", "Nasarawa", "Niger", "Ogun", "Ondo", "Osun", "Oyo", "Plateau", "Rivers", "Sokoto", "Taraba", "Yobe", "Zamfara"]
a = [len(i) for i in states]
indices_sorted = np.argsort(a)[::-1] # [::-1] gives you indices for decreasing order

Output

array([ 8,  3, 24, 35, 19,  1,  2, 30,  5,  4, 10, 16, 17, 33, 32, 31, 22,
   13,  6,  7,  9, 11, 14, 25, 23, 20, 21, 26, 27, 34, 28, 18,  0, 12,
   15, 29])

Now as you can see, the first index in the above output is 8 which means the 9th element of states which is Cross River. Similarly you can access and verify the other elements.

edited Aug 21, 2018 at 9:37

answered Aug 20, 2018 at 14:08

Sheldore

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2 Comments

Godwin Over a year ago

Thanks. I was trying out the bubble sort to try and sort them but this is much easier.

Godwin Over a year ago

Is there a way to create an index which will point out what number belongs to which name in the state list. Like for example, the first 7 could refer to the state "Adamawa".

jh314 · Accepted Answer · 2018-08-20 14:06:20Z

2

You can use a list comprehension:

lengths = [len(state) for state in states]

If you need to use a for loop, create a list and append to it:

lengths = []
for i in states:
    lengths.append(len(i))

answered Aug 20, 2018 at 14:06

jh314

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3 Comments

Godwin Over a year ago

I'm a beginner still learning so pardon my question, but where should I put that in my code?

jh314 Over a year ago

That would replace the for loop

Godwin Over a year ago

aah I get it now. Thanks

Vasilis G. · Accepted Answer · 2018-08-20 14:09:40Z

1

You can also do this using the map function without using a for loop:

a = list(map(len,states))

answered Aug 20, 2018 at 14:09

Vasilis G.

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dorintufar · Accepted Answer · 2018-08-20 14:07:06Z

0

Through generator:

lens = [len(a) for a in states]

answered Aug 20, 2018 at 14:07

dorintufar

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