[REVIEW] Raise duplicate column error in DataFrame.rename
#10120
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galipremsagar
added
bug
Codecov Report
@@ Coverage Diff @@
## branch-22.04 #10120 +/- ##
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+ Coverage 10.37% 10.42% +0.04%
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Files 119 119
Lines 20149 20609 +460
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+ Hits 2091 2148 +57
- Misses 18058 18461 +403
Continue to review full report at Codecov.
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| new_names = ( | ||
| new_col_names = [ | ||
| mapper.get(col_name, col_name) for col_name in self.keys() | ||
| ) | ||
| ] |
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It's not immediately obvious to me - why opt for a list instead of a tuple here?
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This doesn't change a tuple to a list, it changes a generator to a list. There's no equivalent to a list comprehension for a tuple because the syntax (x for x in ...) doesn't create a tuple, it creates a generator. The reason this change is necessary is that you cannot query the length of a generator, so the error check below won't work.
Aside: If you're not familiar with generators, they are what you get when you write a function that uses yield instead of return. The purpose of generators is not to materialize the entire set of data at once, but to instead produce the data one at a time. One of the most obvious uses of this is to save memory, but there are also lots of other reasons you might prefer a generator to a list such as wanting to produce an arbitrary number of elements from an infinite sequence. Here's a simple example illustrating the difference:
>>> def f(x):
... print(f"Called f({x})")
... return x**2
>>> for _ in (f(x) for x in range(3)):
... print("Hello")
...
Called f(0)
Hello
Called f(1)
Hello
Called f(2)
Hello
>>> for _ in [f(x) for x in range(3)]:
... print("Hello")
...
Called f(0)
Called f(1)
Called f(2)
Hello
Hello
Hello
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@gpucibot merge |
galipremsagar
removed
3 - Ready for Review
Fixes: #10117
This PR adds a duplicate column validation check in
ColumnAccessor.rename_levels