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File | Settings | IDE Settings | Editor - Code Completion
From this drop-down list, select the degree to which you want PyCharm to take into consideration the case sensitivity when suggesting matches for code completion. The available options are:
- All: The lookup list includes only those items that match the case of all typed letters. This option is most restrictive.
- None: The lookup list includes all matches regardless of their case.
- First letter: The lookup list includes only the items with the first letter matching.