NBT Parser Minecraft mca file not a gzipped file error

Question

I try to read a Minecraft world with Python from the filesystem and the .mca region/anvil files using the NBT 1.4.1 module (Named Binary Tag Reader/Writer), which is supposed to read the NBT format used in Minecraft. It works fine for files such as level.dat, but throws an error for the region files such as r.0.0.mca

Edit: I am referring to the auto generated world files that minecraft stores in the .minecraft/saves/"MyWorld"/ folder. Such as the level.dat (which works), and the mca files stored in the .minecraft/saves/"MyWorld"/region/ folder such as r.0.0.mca which don't work. I uploaded two sample files from one of my worlds.

Code:

from nbt import nbt level_file = nbt.NBTFile("level.dat", "rb") # works region_file = nbt.NBTFile("r.0.0.mca", "rb")# does not work

Error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.5/dist-packages/nbt/nbt.py", line 508, in __init__
    self.parse_file()
  File "/usr/local/lib/python3.5/dist-packages/nbt/nbt.py", line 532, in parse_file
    type = TAG_Byte(buffer=self.file)
  File "/usr/local/lib/python3.5/dist-packages/nbt/nbt.py", line 85, in __init__
    self._parse_buffer(buffer)
  File "/usr/local/lib/python3.5/dist-packages/nbt/nbt.py", line 90, in _parse_buffer
    self.value = self.fmt.unpack(buffer.read(self.fmt.size))[0]
  File "/usr/lib/python3.5/gzip.py", line 274, in read
    return self._buffer.read(size)
  File "/usr/lib/python3.5/_compression.py", line 68, in readinto
    data = self.read(len(byte_view))
  File "/usr/lib/python3.5/gzip.py", line 461, in read
    if not self._read_gzip_header():
  File "/usr/lib/python3.5/gzip.py", line 409, in _read_gzip_header
    raise OSError('Not a gzipped file (%r)' % magic)
OSError: Not a gzipped file (b'\x00\x00')

Any suggestions how to get this working?

Answer 1

r.0.0.mca is most definitely not compressed. About 80% of the bytes are zeros.

Answer 2

It turns out that the NBT library only supports .mcr region files which have been replaced by .mca files about 6 years ago. However, mcedit is written in Python and supports those files. Due the changes in the Minecraft save format, the interpretation of the content needs to be adjusted though, but the files can be successfully read.