If you don't have a lot of experience with Python you may not know how some of the "magic" parts actually work inside. Some of the things you can do however will end up allocating a lot of memory with extra copies of data that you don't need. If you do that a lot, you will chew through lots of memory. There are often two or more ways of accomplishing the same thing, with one way creating duplicates of data, and the other not. There are valid applications for both, and if you're only dealing with small amounts of data then the differences don't really matter.
Where a lot of people who are new to Python run into problems is that the language is deceptively easy. They try writing Python code that's simply a direct analogue of how they would write Java or C#. The resulting code will run, but it often be slow and a lot more verbose than necessary. Very often the way you would do something in Java or C# is the worst possible way to do it in Python. Conversely, the best way to do it in Python often has no direct analogue in Java or C#. With Python, the learning curve is shallow, but it's very long, and there's lots to learn if you want to reap all the benefits.
Without knowing what your data or algorithms are, it's pretty difficult to give any sensible detailed advice. However, if you are dealing with long "lists" of numbers, perhaps what you really want is long "arrays" of numbers. Lists and arrays are not the same thing in Python.
Where a lot of people who are new to Python run into problems is that the language is deceptively easy. They try writing Python code that's simply a direct analogue of how they would write Java or C#. The resulting code will run, but it often be slow and a lot more verbose than necessary. Very often the way you would do something in Java or C# is the worst possible way to do it in Python. Conversely, the best way to do it in Python often has no direct analogue in Java or C#. With Python, the learning curve is shallow, but it's very long, and there's lots to learn if you want to reap all the benefits.
Without knowing what your data or algorithms are, it's pretty difficult to give any sensible detailed advice. However, if you are dealing with long "lists" of numbers, perhaps what you really want is long "arrays" of numbers. Lists and arrays are not the same thing in Python.