Problem scenario
You installed cv2 with “pip3 install opencv-python”

You run a Python program, but you get this error:

[ERROR:0] global /tmp/pip-req-build-afu9cjzs/opencv/modules/videoio/src/cap.cpp (160) open VIDEOIO(CV_IMAGES): raised OpenCV exception:

OpenCV(4.5.3) /tmp/pip-req-build-afu9cjzs/opencv/modules/videoio/src/cap_images.cpp:253: error: (-5:Bad argument) CAP_IMAGES: can’t find starting number (in the name of file): https://www.youtube.com/watch?v=abcd1234 in function ‘icvExtractPattern’

What should you do?

Possible Solution
The video file is not there.

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Continue reading “How Do You Troubleshoot the Python Error “(-5:Bad argument) CAP_IMAGES: can’t find starting number”?”

Problem scenario
You run this command:

sudo do-release-upgrade

But you see this error:

“Your python3 install is corrupted. Please fix the ‘/usr/bin/python3’ symlink.”

What should you do?

Solution
Run this command:

tail -n 20 /var/log/dist-upgrade/main.log

Do you see a message like this?

2022-03-18 19:36:59,240 DEBUG python symlink points to: ‘python3.5’, but expected is ‘python2.7’ or ‘/usr/bin/python2.7’

If so,

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Continue reading “How Do You Troubleshoot “Your python3 install is corrupted. Please fix the ‘/usr/bin/python3’ symlink.”?”

Problem scenario
You are coding in Python. For some reason your list is getting out of order. It sometimes works. But sometimes the last item is going to the first item. What is wrong?

Possible Solution #1
Re-examine your logic. Break things up into smaller lists and fewer variables for the sake of testing.

Possible Solution #2
Look at the different input files if there are any.

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Continue reading “How Do You Troubleshoot a List in Python That Gets Out of Order?”

Problem scenario
You have a file that is too big to fit into memory. How can Python read the file?

Possible Solution #1
You can use the “open” method and the “read()” or “readlines()” methods. Avoid using read() because that will read the entire file into memory. The readline() and readlines() methods can be given a byte number as an argument.

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Continue reading “How Do You Write a Python Program to Process a Large File?”

Problem scenario
In Python if you test if a value is in a dictionary, does it look at the keys, the values, or both?

For example, you have code like this:

good_kv = {}
good_kv[”a”] = 1
good_kv[”b”] = 2
good_kv[”c”] = 3

if “b” in good_kv:
print(“The value is in the dictionary!”)
else:
print(“The value is not in the dictionary!”)

print (“testing keys of dictionary above and values of dictionaries below”)

if 3 in good_kv:
print(“The value is in the dictionary!”)
else:
print(“The value is not in the dictionary!”)

Do dictionaries keys,

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Continue reading “Do “if x in dic” Statements Look at Keys or Values in Python Dictionaries?”