tinydb:Empty query was evaluated - mysql

Question

One of the things this below code does is put different student IDs in tiny database after checking if the new ID is already present or not.
Code's below -
#enroll.py
# USAGE
# python enroll.py --id S1901 --name somename --conf config/config.json
# import the necessary packages
from pyimagesearch.utils import Conf
from imutils.video import VideoStream
from tinydb import TinyDB
from tinydb import where
import face_recognition
import argparse
import imutils
import pyttsx3
import time
import cv2
import os
# construct the argument parser and parse the arguments
ap = argparse.ArgumentParser()
ap.add_argument("-i", "--id", required=True,
help="Unique student ID of the student")
ap.add_argument("-n", "--name", required=True,
help="Name of the student")
ap.add_argument("-c", "--conf", required=True,
help="Path to the input configuration file")
args = vars(ap.parse_args())
# load the configuration file
conf = Conf(args["conf"])
# initialize the database and student table objects
db = TinyDB(conf["db_path"])
studentTable = db.table("student")
# retrieve student details from the database
student = studentTable.search(where(args["id"]))
# check if an entry for the student id does *not* exist, if so, then
# enroll the student
if len(student) == 0:
# initialize the video stream and allow the camera sensor to warmup
print("[INFO] warming up camera...")
vs = VideoStream(src=0).start()
time.sleep(2.0)
# initialize the number of face detections and the total number
# of images saved to disk
faceCount = 0
total = 0
# ask the student to stand in front of the camera
print("{} please stand in front of the camera until you" \
"receive further instructions".format(args["name"]))
# initialize the status as detecting
status = "detecting"
# create the directory to store the student's data
os.makedirs(os.path.join(conf["dataset_path"], conf["class"],
args["id"]), exist_ok=True)
# loop over the frames from the video stream
while True:
# grab the frame from the threaded video stream, resize it (so
# face detection will run faster), flip it horizontally, and
# finally clone the frame (just in case we want to write the
# frame to disk later)
frame = vs.read()
frame = imutils.resize(frame, width=400)
frame = cv2.flip(frame, 1)
orig = frame.copy()
# convert the frame from from RGB (OpenCV ordering) to dlib
# ordering (RGB) and detect the (x, y)-coordinates of the
# bounding boxes corresponding to each face in the input image
rgb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
boxes = face_recognition.face_locations(rgb,
model=conf["detection_method"])
# loop over the face detections
for (top, right, bottom, left) in boxes:
# draw the face detections on the frame
cv2.rectangle(frame, (left, top), (right, bottom),
(0, 255, 0), 2)
# check if the total number of face detections are less
# than the threshold, if so, then skip the iteration
if faceCount < conf["n_face_detection"]:
# increment the detected face count and set the
# status as detecting face
faceCount += 1
status = "detecting"
continue
# save the frame to correct path and increment the total
# number of images saved
p = os.path.join(conf["dataset_path"], conf["class"],
args["id"], "{}.png".format(str(total).zfill(5)))
cv2.imwrite(p, orig[top:bottom, left:right])
total += 1
# set the status as saving frame
status = "saving"
# draw the status on to the frame
cv2.putText(frame, "Status: {}".format(status), (10, 20),
cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 0, 0), 2)
# show the output frame
cv2.imshow("Frame", frame)
cv2.waitKey(1)
# if the required number of faces are saved then break out from
# the loop
if total == conf["face_count"]:
# let the student know that face enrolling is over
print("Thank you {} you are now enrolled in the {} " \
"class.".format(args["name"], conf["class"]))
break
# insert the student details into the database
studentTable.insert({args["id"]: [args["name"], "enrolled"]})
# print the total faces saved and do a bit of cleanup
print("[INFO] {} face images stored".format(total))
print("[INFO] cleaning up...")
cv2.destroyAllWindows()
vs.stop()
# otherwise, a entry for the student id exists
else:
# get the name of the student
name = student[0][args["id"]][0]
print("[INFO] {} has already already been enrolled...".format(
name))
# close the database
db.close()
ISSUE:
While i run this code for the 1st time, everything works fine.
>> python3 enroll.py --id S1111 --name thor --conf config/config.json
I get my ID in my json file as shown below -
{"student": {"1": {"S1111": ["thor", "enrolled"]}}}
But when i try to put another ID -
python3 enroll.py --id S1112 --name hulk --conf config/config.json
I get the following error -
ERROR:
Traceback (most recent call last):
File "enroll.py", line 35, in <module>
student = studentTable.search(where(args["id"]))
File "/usr/lib/python3.5/site-packages/tinydb/table.py", line 222, in search
docs = [doc for doc in self if cond(doc)]
File "/usr/lib/python3.5/site-packages/tinydb/table.py", line 222, in <listcomp>
docs = [doc for doc in self if cond(doc)]
File "/usr/lib/python3.5/site-packages/tinydb/queries.py", line 59, in __call__
return self._test(value)
File "/usr/lib/python3.5/site-packages/tinydb/queries.py", line 136, in notest
raise RuntimeError('Empty query was evaluated')
RuntimeError: Empty query was evaluated
If i change my table name from student to something else then again it will store id only for the first time then gives the same error. I'm not sure what's wrong here.