[mypyc] Implement `str.lower()` and `str.upper()` primitive #19375

Jahongir-Qurbonov · 2025-07-04T08:42:46Z

Add primitive for str.lower and str.upper. Issue: mypyc/mypyc#1088

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JukkaL

Thanks for the PR! Left some comments -- the semantics are pretty tricky, and we need to be careful to catch all special cases. I'd suggest running a test (doesn't need to be included in this PR necessarily) comparing upper/lower of all length-1 strings with Python semantics.

mypyc/lib-rt/str_ops.c

JukkaL · 2025-07-04T16:04:29Z

mypyc/test-data/run-strings.test

+    assert "abc".lower() == "abc"
+    assert "AbC123".lower() == "abc123"
+    assert "áÉÍ".lower() == "áéí"
+    assert "😴🚀".lower() == "😴🚀"


Also test special cases (verify that this agrees with normal Python semantics):

'SS'.lower() == 'ss'

'Σ'.lower()

'İ'.lower() (changes length!)

JukkaL · 2025-07-04T16:11:17Z

mypyc/test-data/run-strings.test

+    assert "ABC".upper() == "ABC"
+    assert "AbC123".upper() == "ABC123"
+    assert "áéí".upper() == "ÁÉÍ"
+    assert "😴🚀".upper() == "😴🚀"


Also test special case (verify that this agrees with normal Python semantics):

'ß'.upper() == 'SS'

'ﬃ'.upper() (length increases!)

… logic for non-ASCII characters

…fallback logic and using direct table lookups

…static lookup tables and using direct character conversion

…ing for character conversion

…e special characters

BobTheBuidler · 2025-08-16T20:46:06Z

@JukkaL he never unmarked this as a draft, but I notice he added the tests you requested. Is there anything left blocking this one? I would find this quite helpful for my use cases so I am willing to finish it up if there's anything else.

Jahongir-Qurbonov · 2025-08-17T11:01:34Z

@BobTheBuidler These have not passed the test successfully, I don't know when I will have time, you can continue with this

#assert "İ".lower() == "i̇"  # TODO: Latin capital letter I with dot above -> 'i' + combining dot
#assert len("İ".lower()) == 2  # TODO: Confirms length change

#assert "ß".upper() == "SS"     # TODO: German sharp S -> double S
#assert "ﬃ".upper() == "FFI"    # TODO: Ligature 'ffi' -> separate letters
#assert len("ﬃ".upper()) == 3   # TODO: Confirm length increases

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Add str.lower() and str.upper() primitives

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Jahongir-Qurbonov changed the title ~~Add str.lower() and str.upper() primitives~~ [mypyc] Implement str.lower() and str.upper() primitive Jul 4, 2025

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sterliakov added the topic-mypyc mypyc bugs label Jul 4, 2025

JukkaL reviewed Jul 4, 2025

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Jahongir-Qurbonov marked this pull request as draft July 4, 2025 18:08

Jahongir-Qurbonov and others added 8 commits July 6, 2025 16:42

Refactor tolower_ucs4 and toupper_ucs4 functions by removing fallback…

8065f9c

… logic for non-ASCII characters

Optimize CPyStr_Lower and CPyStr_Upper for ASCII strings by removing …

1d40499

…fallback logic and using direct table lookups

Optimize CPyStr_Lower and CPyStr_Upper for ASCII strings by removing …

2750549

…static lookup tables and using direct character conversion

Add test case for lower() method with special case for uppercase 'SS'

62520ef

Refactor CPyStr_Lower and CPyStr_Upper to use consistent variable nam…

cc2ed14

…ing for character conversion

Add test case for lower() method to handle Greek capital sigma

5cdca5a

Add commented-out test cases for lower() and upper() methods to handl…

7049d8b

…e special characters

Merge branch 'python:master' into str-lower-upper

bd4bde2

Jahongir-Qurbonov and others added 2 commits August 17, 2025 16:06

Merge branch 'master' into str-lower-upper

b8fe8f5

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Jahongir-Qurbonov marked this pull request as ready for review August 17, 2025 12:27

Jahongir-Qurbonov requested a review from JukkaL August 17, 2025 12:27

Jahongir-Qurbonov added 2 commits August 21, 2025 15:52

Merge branch 'master' into str-lower-upper

86abdde

Merge branch 'master' into str-lower-upper

2ae0353

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[mypyc] Implement `str.lower()` and `str.upper()` primitive #19375

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[mypyc] Implement `str.lower()` and `str.upper()` primitive #19375

[mypyc] Implement `str.lower()` and `str.upper()` primitive #19375