Cleaning system cache
PyCharm caches a great number of files, therefore the system cache may become overloaded. Sometimes the caches will never be needed again, for example, if you work with frequent short-term projects. Also, the only way to solve some conflicts is to clean out the cache.
In the Invalidate Caches dialog, select the relevant action. You can invalidate the caches and restart the IDE or just restart the IDE.
For more information about various user-specific files, refer to Directories used by the IDE.