[SPARK-3985] [Examples] fix file path using os.path.join

[adrian-wang]

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[adrian-wang]

retest this please.

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QA tests have started for PR 2834 at commit da7aa95.

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[srowen]

Is it maybe simpler to just add a / ? This makes it look like the path is platform independent but it isn't as the following path always has /

[adrian-wang]

I was just trying to make this consistent with other code in python/pyspark/**.py. It is OK if you believe add a '/' is better.

[srowen]

Consistency is good too. Leave it unless someone else thinks it should change.

[JoshRosen]

I think the os.path.join is fine; I think it's more clear / less brittle. If it turns out that we do need to make changes to the path separator in order to support Windows, then using os.path.join makes it easier to spot where path construction is taking place in order to find the code that needs to be changed.

[JoshRosen]

LGTM. Thanks for catching this!