Sure they do.

> To minimise some Python code you need almost an entire Python parser.

I don't think source-to-source transformations requiring a parser for the source is an indication that it is problematic for computers to handle something. I mean, to execute the source code you need a parser, too, and no one says that needing a parser for execution is a sign that computers don't handle a language well.

> Assembling Python code from small pieces (something that is really important for Javascript) is a frightening problem.

Sure, assembling by cut-and-paste is a problem with significant indentation, especially when using media (like the web) which do not respect indentation well.

OTOH, using significant amount of cut-and-paste coding (rather than reuse by library code) is a sign of a problem with the language, development process, and/or execution environment, anyway, so I don't see it as a particular problem that a language structure isn't friendly to copy-paste coding.