Modify feature class file name using f string

[SeanLukacs]

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!

[DanPatterson · Accepted solution]

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']

[HaydenWelch · Accepted solution]

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"

[SeanLukacs]

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?

[HaydenWelch]

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'

[SeanLukacs]

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

[SeanLukacs]

Thank you!

[TylerT]

@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

[SeanLukacs]

@TylerT Thanks for that!  

[TylerT]

@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