For loop through a numpy array of strings

Question

I imported a csv file containing zip codes as a string using the following line:

my_data = genfromtext('path\to\file.csv', delimiter = ',', dtype=str, autostrip=True)

I am importing as a string in order to keep the leading zeroes some zip codes may contain. Now I need to also loop through the entire numpy array and I wanted to do so like this:

for i in np.nditer(my_data): 
     do something with my_data[i]

But unfortunately it is returning the following error:

Arrays used as indices must be of integer (or boolean) type

Any idea how I can loop through each element of this numpy array?

Mike Müller · Accepted Answer · 2017-11-30 15:29:01Z

1

While looping over NumPy arrays is often not a good solution, you can do it like this:

for i in range(len(my_data)): 
     do something with my_data[i]

You might be better off reading your data into a list, process the strings, and convert into NumPy array afterwards.

edited Nov 30, 2017 at 15:29

answered Nov 30, 2017 at 15:16

Mike Müller

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3 Comments

Macterror Over a year ago

This actually worked! Although it looks like its pretty slow, processing about 3 zips per second. Would you happen to know a faster way by any chance?

Mike Müller Over a year ago

In NumPy you want whole-array operations. It depends very much the do something actually does if you can do it without loops.

Macterror Over a year ago

Thanks I will definitely look more into it

user3598726 · Accepted Answer · 2017-11-30 15:17:31Z

1

You should do something with i, not with my_data[i]. i is already your element (a part if mydata). Thats why my_data[i] is not working, becouse i is not an index. it is a numpy array.

If you want to use index, and the given element too, use enumerate()

Example:

lista = [20,50,70]
for idx, element in  enumerate(lista): 
    print (idx, element)

For more info visit this site numpy iteration tutorial

answered Nov 30, 2017 at 15:17

user3598726

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