topic Re: Modify feature class file name using f string in Python Questions

Modify feature class file name using f string

SeanLukacs — Tue, 19 Aug 2025 19:11:03 GMT

Hello, I am pretty new with using python in Pro. I need to modify feature class output names as they are being generated, or after they are created.

I have a list of features in a feature dataset (since this is a list, I am assuming using listFeatureClass, for loop, and f strings is how I cycle through the layers)

EX_feature1

EX_feature2

EX_feature3

I want to remove the "EX_" from the feature class name and add "TR" in its place.

Is this a strip function? can that be applied to fc names? Thanks in advance!

Re: Modify feature class file name using f string

DanPatterson — Tue, 19 Aug 2025 19:21:34 GMT

replace should work

fcs = ["c:/path/EX_feature1","c:/path/EX_feature2", "c:/path/EX_feature3"] out_fcs = [i.replace("EX_", "TR") for i in fcs] out_fcs ['c:/path/TRfeature1', 'c:/path/TRfeature2', 'c:/path/TRfeature3']

Re: Modify feature class file name using f string

HaydenWelch — Wed, 20 Aug 2025 04:41:13 GMT

If you know you just need to replace the first 3 characters (say it was a state code with an underscore or something) you could also do:

out_fcs = [f"TR{fc[3:]}" for fc in fcs]

Using replace can sometimes burn you since by default it replaces *all* matching substrings unless you specify a limit. Meaning "aaabbbaaa".replace("a", "b") will give you "bbbbbbbbb" or "tr_tracks".replace("tr", "ex") would give you "ex_exacks"

Re: Modify feature class file name using f string

SeanLukacs — Wed, 20 Aug 2025 12:46:21 GMT

Thank you!

Re: Modify feature class file name using f string

TylerT — Wed, 20 Aug 2025 13:03:51 GMT

@SeanLukacs,
If you need a bit more robustness on future data sets you could look at regex substitution (re.sub()). re.sub() will gracefully handle start matches, multiple matches, and non-matches with about the same amount of code. Here's an example:

import re fcs = [ "EX_feature1", "EX_feature2", "feature4", "EX_feature5_EX_", ] print(f"Original: {fcs}") print(f'string replace: {[i.replace("EX_", "TR_") for i in fcs]}') print(f'string slicer: {[f"TR_{fc[3:]}" for fc in fcs]}') print(f"regex substitution: {[re.sub(r'^EX_', 'TR_', fc) for fc in fcs]}")

Output:

Original: ['EX_feature1', 'EX_feature2', 'feature4', 'EX_feature5_EX_'] string replace: ['TR_feature1', 'TR_feature2', 'feature4', 'TR_feature5_TR_'] string slicer: ['TR_feature1', 'TR_feature2', 'TR_ture4', 'TR_feature5_EX_'] regex substitution: ['TR_feature1', 'TR_feature2', 'feature4', 'TR_feature5_EX_']

<Note: I changed from required 'TR' to 'TR_' for readability in this example only.>

HTH,

Tyler

Re: Modify feature class file name using f string

SeanLukacs — Wed, 20 Aug 2025 12:50:54 GMT

Thank you! Is your example setting the output variable? So I am clipping several layers and then renaming them to exclude the first 3 characters and replace with a different amount of characters, would that still work?

ex. "EX_" gets removed and I add in "TR100yr_". so then my version of your line looks like outFeature = [f"TR100yr_{fc[3:]}" for fc in fcs]. Is the "3" just the number of characters to replace or an index?

Re: Modify feature class file name using f string

SeanLukacs — Wed, 20 Aug 2025 13:08:20 GMT

@TylerT Thanks for that!

Re: Modify feature class file name using f string

HaydenWelch — Wed, 20 Aug 2025 16:33:56 GMT

It is! In Python, strings implement the Sequence protocol, so you can iterate them and slice them like lists. The [3:] syntax is a slice that starts after the 3rd element and runs to the end. you can also truncate the last 3 with [3:-3] or get every other character between the first and last 3 with [3:-3:2]

>>> text = "abc_hello-world" >>> text[3:] ... '_hello-world' >>> text[3:-3] ... '_hello-wo' >>> text[3:-3:2] ... '_el-o'

Re: Modify feature class file name using f string

SeanLukacs — Wed, 20 Aug 2025 19:18:57 GMT

@HaydenWelch That seemed to do the trick for my use case, thank you!

Re: Modify feature class file name using f string

TylerT — Tue, 26 Aug 2025 17:20:05 GMT

@SeanLukacs ,
I noticed in the Python docs that `string.replace()` has an optional count keyword giving it a bit more flexibility. If keyword count is passed, only the first count occurrences are replaced. This might be useful for your case also.

Tyler