Selecting characters in string numpy array (Python)

Question

I have a numpy.ndarray of strings like that

HHMM = ['0000' '0001' '0002' '0003' '0004' '0005' '0006' '0007' '0008' '0009' ...]

Here the first two elements are the hour and the last two the minute. In order to convert to time format (using datetime), I want to separate this characters.

I tried doing

hour   = HHMM[::][0:2]
minute = HHMM[::][2:4]

but the result is this

print hour
['0000' '0001']

print minute
['0002' '0003']

What is your expected result? Do you want to end up with an array of datetime64 values or just arrays of strings? — Alex Riley
– Alex Riley, Commented Feb 4, 2016 at 12:34
I want to split the two first and the two last characters (hours and minutes strings) in order to convert in a integer individuallly. Once this was made, I can make a map and convert them in datetime format. I only need to separate in individually arrays. — nandhos
– nandhos, Commented Feb 4, 2016 at 12:39
HHMM.view('S2,S2') might split it into a 2 field structured array. — hpaulj
– hpaulj, Commented Feb 4, 2016 at 12:48

Colonel Beauvel · Accepted Answer · 2016-02-04 12:38:14Z

4

Why not simple comprehension lists:

[u[:2] for u in HHMM]
#Out[39]: ['00', '01', '02', '03', '04', '05', '06', '07', '08', '09']

[u[-2:] for u in HHMM]
#Out[40]: ['00', '01', '02', '03', '04', '05', '06', '07', '08', '09']

answered Feb 4, 2016 at 12:38

Colonel Beauvel

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e.doroskevic · Accepted Answer · 2016-02-04 12:51:21Z

1

Example:

for i in range(len(HHMM)):
    hour = HHMM[i][0:2]
    minute = HHMM[i][2:]
    print('Time: {}:{}'.format(hour, minute))

Output:

Time: 00:00
Time: 00:01
Time: 00:02
Time: 00:03
Time: 00:04
Time: 00:05
Time: 00:06
Time: 00:07
Time: 00:08
Time: 00:09

EDIT:

HHMM = ['0000', '0001', '0002', '0003', '0004', '0005', '0006', '0007', '0008', '0009']

hours = []
minutes = []

for i in range(len(HHMM)):
    hours.append(HHMM[i][0:2])
    minutes.append(HHMM[i][2:])

print('Hours: {}'.format(list(hours)))
print('Minutes: {}'.format(list(minutes)))

edited Feb 4, 2016 at 12:51

answered Feb 4, 2016 at 12:25

e.doroskevic

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4 Comments

nandhos Over a year ago

This only print the values, hour is not an array, still when I define hour = [ ] before making the iteration. The same for minute. When print hour and minute, just print the last value.

e.doroskevic Over a year ago

@nandhos dude, here you go - is this what you wanted? Now hours and minutes are a type of collection

nandhos Over a year ago

sorry, I missed append!

e.doroskevic Over a year ago

@nandhos no worries man, thank you for acknowladging my contribution ;D

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