Python-OpenCV --F Function error--not finding right dir

Question

Am trying to put a timelapse on my OpenCV code but it seems i am doing something that is not right and i don't know why i have the error. The erorr i got is for this line: filename = f"{timelapse_img_dir}/{i}.jpg" What should i do in order not to have an error?

This is the error i have from my IDE:

File "/Users/Dropbox/OpenCV/src/timelapse.py", line 34
    filename        = f"{timelapse}/{i}.jpg"
                                           ^
SyntaxError: invalid syntax
[Finished in 0.1s with exit code 1]
[shell_cmd: python -u "/Users/Dropbox/OpenCV/src/timelapse.py"]
[dir: /Users/Dropbox/OpenCV/src]
[path: /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin]

My code:

import os
import numpy as np
import cv2
import time
import datetime

from utils import CFEVideoConf, image_resize
import glob

cap = cv2.VideoCapture(0)


frames_per_seconds = 20
save_path='saved-media/timelapse.mp4'
config = CFEVideoConf(cap, filepath=save_path, res='720p')
out = cv2.VideoWriter(save_path, config.video_type, frames_per_seconds, config.dims)
timelapse_img_dir = '/Users/Dropbox/OpenCV/src/images/timelapse/'
seconds_duration = 20
seconds_between_shots = .25

if not os.path.exists(timelapse_img_dir):
    os.mkdir(timelapse_img_dir)

now = datetime.datetime.now()
finish_time = now + datetime.timedelta(seconds=seconds_duration)
i = 0
while datetime.datetime.now() < finish_time:
    '''
    Ensure that the current time is still less
    than the preset finish time
    '''
    ret, frame      = cap.read()
    # filename        = f"{timelapse_img_dir}/{i}.jpg"
    filename        = f"{timelapse_img_dir}/{i}.jpg"
    i               += 1
    cv2.imwrite(filename, frame)
    time.sleep(seconds_between_shots)
    if cv2.waitKey(20) & 0xFF == ord('q'):
        break


def images_to_video(out, image_dir, clear_images=True):
    image_list = glob.glob(f"{image_dir}/*.jpg")
    sorted_images = sorted(image_list, key=os.path.getmtime)
    for file in sorted_images:
        image_frame  = cv2.imread(file)
        out.write(image_frame)
    if clear_images:
        '''
        Remove stored timelapse images
        '''
        for file in image_list:
            os.remove(file)

images_to_video(out, timelapse_img_dir)
# When everything done, release the capture
cap.release()
out.release()
cv2.destroyAllWindows()

Elad · Accepted Answer · 2018-05-27 12:18:21Z

2

I believe the format you are using is only supported on python 3.6 "Literal String Interpolation":

https://www.python.org/dev/peps/pep-0498/#raw-f-strings

filename  = f"{timelapse_img_dir}/{i}.jpg"

here are 2 other options depends on what python you are using:

python 2.7:

filename = '%(timelapse_img_dir)s %(i)s' % locals()

python 3+

filename = '{timelapse_img_dir} {i}'.format(**locals())

Based on: https://pyformat.info/

edited May 27, 2018 at 12:18

answered May 27, 2018 at 11:19

Elad

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5 Comments

Cohen Over a year ago

Thank you Elad! And this line of code, how is transforming? image_list = glob.glob(f"{image_dir}/*.jpg")

Elad Over a year ago

what python version are you using?

Cohen Over a year ago

3 Elad! thanks! and in my code i want to have different images saved as jpg in a timelapse dir. Does this part of code save as jpg, 's' % locals()'

Elad Over a year ago

@cohen, "%(..)s" % locals is for python 2.7 and is just transforming a local defined variable to a string

Cohen Over a year ago

so my timelapse_img_dir = "/Users/Dropbox/OpenCV/src/images/timelapse/". i just need to format in this folder jpg images starting from 1 to infinite. My code is for dir/1.jpg. is this right for filename = '{timelapse_img_dir} {i}'.format(**locals())? i dont find the jpg extension here.

Cohen · Accepted Answer · 2018-05-27 19:02:44Z

1

I dont know why i was not able to use the f function. I had to do another concatenation to work.

 filename        = timelapse_img_dir +str(i) +file_format

and for the rest i used the wild card

filetomake = image_dir + "/*.jpg"

    image_list = glob.glob(filetomake)

answered May 27, 2018 at 19:02

Cohen

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