NoneType object is not iterable

Question

I am getting a 'NoneType' object is not iterable TypeError in the code below. The code below is ment to use pyautogui to scroll through 10 images in the digits folder (named 0 through 9, named with the # in the image) and when ever it finds one, report the value of x along with the number it found. The dictionary is then sorted by x values to read the number found in the image.

Question: I am still learning Python and this TypeError has me stomped, how can I correct this?

#! python3
import sys
import pyautogui

# locate Power
found = dict()
for digit in range(10):
    positions = pyautogui.locateOnScreen('digits/{}.png'.format(digit),
                                         region=(888, 920, 150, 40), grayscale=True)
    for x, _, _, _ in positions:
        found[x] = str(digit)
cols = sorted(found)
value = ''.join(found[col] for col in cols)
print(value)

Traceback of the error:

Traceback (most recent call last):
  File "C:\Users\test\python3.6\HC\power.py", line 10, in <module>
    for x, _, _, _ in positions:
TypeError: 'NoneType' object is not iterable

Sounds like `pyautogui.locateOnScreen()` returned `None`. What is the *full* traceback of the error? — Martijn Pieters, Mar 13 '17 at 00:44
Sorry I added it to the main post. This was the first question I ever posted about python so I wasnt sure if you needed it all to help :-) — Brandon, Mar 13 '17 at 00:46
Yup, `pyautogui.locateOnScreen()` returned `None`, so `for ... in positions` fails as you can't loop over `None`. It means nothing was found. — Martijn Pieters, Mar 13 '17 at 00:47
Ahh, changing to locateAllOnScreen gets rid of the error but then returns nothing :-( So either there is an issue with my positions line, or an issue with my value line that is supposed to put all of the results together. — Brandon, Mar 13 '17 at 00:53
I guess I shall need to open another post to find out if my code to look through the digits folder is correct — Brandon, Mar 13 '17 at 00:54
Possible duplicate of [TypeError: 'NoneType' object is not iterable in Python](http://stackoverflow.com/questions/3887381/typeerror-nonetype-object-is-not-iterable-in-python) — Kevin J. Chase, Mar 13 '17 at 02:48

score 8 · Accepted Answer · answered Mar 13 '17 at 01:06

You need to add check for None prior iteration through your positions

#! python3
import sys
import pyautogui 

# locate Power
found = dict()
for digit in range(10):
    positions = pyautogui.locateOnScreen('digits/{}.png'.format(digit), region=(888, 920, 150, 40), grayscale=True)
    if positions is not None: 
        for x, _, _, _ in positions:
            found[x] = str(digit)
cols = sorted(found)
value = ''.join(found[col] for col in cols)
print(value)

NoneType object is not iterable

1 Answers1