Need help in Understanding Code Logic

Part 1 (2020)
1

Hi,

What’s the logic behind the if condition in the below code?

2021-11-07_11-36

My understanding :

  • Line 5 : path.exists() - Returns True
  • Line 5 : not path.exists() - Returns False
  • Line 5 : if not path.exists() - Isn’t it the same as if False ??
    So, when if not path.exists() is False - How would the next line of code path.mkdir() execute??

Also, can we use the code path.mkdir(exist_ok=True) instead of
if not path.exists(): path.mkdir()
What is the difference between the 2 codes?

  • Line 11 : results=search_images_ddg(...) - In this code - we are not specifying the path to the individual directories of the 3 Categories of bears (grizzly,black,teddy). Then how are the images fetched & stored in the respective folders??

Can anyone please help me understand all the above??

Another issue with the above code :

This code is not working most of the time i.e. It is returning 0 images most of the times which can be confirmed using the below code :

fns = get_image_files(path)
fns
fns returns this : (#0) []

Only once did the code work fine returning 282 images.

This behavior is seen when I am trying the code in the Jarvis Labs console.

1
1988×648 58.6 KB

However, when I try the same code in Jupyter Lab locally its working fine & returning ample images.

2
2854×571 58.8 KB

Could anyone please guide me the reason behind the variation in results of the same code in different scenarios!!

Thanx in advance!!

2

line 5 explanation

# path.exists() returns true if path exists, else false, let us consider path didn't exists returns false, if not False: becomes if True, so dir will be created.
if not path.exists(): 
   path.mkdir()

Q: Also, can we use the code path.mkdir(exist_ok=True) instead of if not path.exists(): path.mkdir() What is the difference between the 2 codes?

  • you can use either of those methods, both creates directory if it didn’t exist

Q: Line 11 : results=search_images_ddg(…) - In this code - we are not specifying the path to the individual directories of the 3 Categories of bears (grizzly,black,teddy). Then how are the images fetched & stored in the respective folders??

  • search_images_ddg(key) function only returns list of urls, afterwards we need to call download_images(destination_path, urls=results.attrgot('contentUrl') , to download images, so only get_image_files(path) returns empty list.
  • maybe in your local environment you have already downloaded images so only you are getting 300 as result.
3

Hi Siva,

Thank you so much for your help!

Thanx for pointing out to the download_images logic.
My code is working fine now & the final result has ample images.

2 Issues!!

Issue 1 :

I understood the if condition logic.

But when below is the case
path = Path('bears') - Path created i.e. path.exists()=True
then,
if not path.exists(): - This condition becomes False
path.mkdir() - And, this code shouldn’t execute! Right!!

Is it so??

But, inspite of the fact that if not path.exists() is False - the next line path.mkdir() is still executing fine without throwing any error!!

How is it so??

Issue 2 :

Case 1:
Line 1 : path = Path('bears')
Line 2 : path.mkdir(exist_ok=True)

Case 2:
Line 1 : dest = (path/x)
Line 2 : dest.mkdir(exist_ok=True)

What’s the difference between Line1 & Line 2 in both the above cases??
What does each line do??

My code is running absolutely fine without throwing any errors & am getting ample images at the end - Even if I do not mention the 2nd Line.

Please see the below image where Line 2 mentioned in both the above 2 cases, is Commented out (Line 2 & Line 8) in the code - But still the code runs fine & gives the desired result.

2021-11-07_11-36
2021-11-07_11-36788×388 43.5 KB

I am getting the same results irrespective of mentioning those lines or commenting them i.e. Line 2 & Line 8 in the above image.

Can you please explain.

Thanx again for all the help!!

4

@Vnay0007 , Please check this github gist pathlib_path.ipynb · GitHub for better understanding.

5

@sirakr Thanx a lot!! Truly appreciate the effort. :pray: