PyCIFRW

5.0.1 verified Sat May 09 auth: no python

PyCIFRW provides support for reading and writing CIF (Crystallographic Information File) and STAR files in Python. Version 5.0.1 is the latest stable release, with a focus on bugfixes and dropping Python 2 support. The library is maintained with occasional releases.

pip install pycifrw

Common errors

error ModuleNotFoundError: No module named 'pycifrw' ↓

cause Trying to `import pycifrw` or `from pycifrw import ...`. The top-level module is not 'pycifrw'—the actual modules are CifFile, StarFile, etc.

fix

Install with pip install pycifrw but import from 'CifFile' (e.g., from CifFile import ReadCif).

error SyntaxError: invalid syntax (for print statements, etc.) ↓

cause Running Python 2 code on Python 3. PyCIFRW 5+ requires Python 3.

fix

Ensure Python 3 interpreter is used (python3). If stuck on Python 2, install pycifrw==4.4.6.

error AttributeError: 'CifFile' object has no attribute 'keys' ↓

cause Reading a CIF file with errors; the object may be incomplete. Or using wrong method to access data.

fix

Use ReadCifWithError to get partial results, or check the CIF syntax. Access data via ast.first_loop()['_tag'] or convert to dict: dict(ast.items()).

Warnings

breaking Version 5.0 dropped Python 2 support entirely. Code written for Python 2 will not run. ↓

fix Upgrade to Python 3, or pin to pycifrw==4.4.6 if stuck on Python 2.

deprecated The function `ReadCif` still works but `ReadCifWithError` is recommended for more robust parsing. ↓

fix Use `from CifFile import ReadCifWithError` and handle returned parse info.

gotcha Importing from `pycifrw` directly fails. The correct import path is `CifFile`, `StarFile`, etc. ↓

fix Use `from CifFile import ReadCif` instead of `from pycifrw import ReadCif`.

Imports

ReadCif
wrong
```
from pycifrw import ReadCif
```
correct
```
from CifFile import ReadCif
```
Common mistake: users try to import from the top-level package name.

CifFile

wrong

from pycifrw import CifFile

correct

from CifFile import CifFile

Import path is CifFile, not pycifrw.

StarFile
```
from StarFile import StarFile
```

Quickstart

Read a CIF file and print the top-level keys. Note: the input CIF must exist. For demo, we write a minimal CIF first.

from CifFile import ReadCif
# Replace with an actual CIF file path or content
cif_content = """data_test
_audit_creation_method 'manually created'
"""
with open('test.cif', 'w') as f:
    f.write(cif_content)
ast = ReadCif('test.cif')
print(ast.keys())
# Clean up
import os
os.remove('test.cif')