os.path.exists returns false but not raising exception in try/except block

Question

I'm trying to validate a list of input directories and want the script to raise errors if the directories do not exist. I don't believe if-not will work here since if these folders do not exist (with the required input files [I have another validation for this]) then the script cannot run.

folder1 = "d:\\temp\\exists"
folder2 = "d:\\temp\\notexists"
list = [folder1, folder2]
list #gives ['d:\\temp\\exists', 'd:\\temp\\notexists']

for l in list:
    try:
        os.path.exists(l)
        print("{0} folder exists...".format(l))
    except FileNotFoundError:
        print("{0} folder does not exist!".format(l))

os.path.exists correctly identifies folder2 as not existing, but does not raise an exception:

True
d:\temp\exists folder exists...
False
d:\temp\notexists folder exists...

You can reach that code without errors, so the code will not go to the exception block. The path.exists gives a boolean that tells you if a path exists, so even when it does not — chatax, Feb 20 '20 at 16:42
Calling ``os.path.exists`` does not raise any errors if the file does not exist (it just returns ``False``). Why do you think ``FileNotFoundError`` would be raised in your code? — MisterMiyagi, Feb 20 '20 at 17:06
You could raise a generic exception like in [this answer](https://stackoverflow.com/a/29954408/11764049) — Aelius, Apr 29 '21 at 13:58

chatax · Accepted Answer · 2020-02-20T17:03:46.283

4

If you want the code to stop and raise an error:

for l in list: 
    if os.path.exists(l): 
        print("{0} folder exists...".format(l))
   else:
      raise FileNotFoundError("{0} folder does not exist!".format(l))

edited Feb 20 '20 at 17:03

answered Feb 20 '20 at 16:47

chatax

990
3
17

I want it to stop the code and raise an error. Thanks. – Clickinaway Feb 20 '20 at 16:56

score 0 · Answer 2 · answered Feb 20 '20 at 16:46

0

if...else block should do the trick

folder1 = "d:\\temp\\exists"
folder2 = "d:\\temp\\notexists"
list = [folder1, folder2]
list #gives ['d:\\temp\\exists', 'd:\\temp\\notexists']

for l in list:
    if os.path.exists(l)
        print("{0} folder exists...".format(l))
    else:
        print("{0} folder does not exist!".format(l))

answered Feb 20 '20 at 16:46

Prachiti Prakash Prabhu

654
1
5
16

if the folders are not present, the rest of the code cannot run properly. Thanks. – Clickinaway Feb 20 '20 at 16:57

os.path.exists returns false but not raising exception in try/except block

2 Answers2