如何用Python从PosixPath逐个读取20000个DICOM文件？

Hey there! Let's tackle this DICOM file reading issue with your PosixPath objects. I’ve run into similar scenarios when processing large batches of medical images, so here are the most common fixes and best practices to get you back on track:

Most DICOM parsing libraries (like pydicom, the most popular one for Python) expect a string path rather than a raw PosixPath object. This is the #1 culprit for errors in this scenario.

• ❌ Wrong approach: Directly passing the PosixPath

  import pydicom
  ds = pydicom.dcmread(my_posix_path)  # Likely throws an error
  

• ✅ Correct approaches:

  # Convert to standard string
  ds = pydicom.dcmread(str(my_posix_path))
  
  # Or use as_posix() to get a POSIX-style string (forward slashes)
  ds = pydicom.dcmread(my_posix_path.as_posix())
  

With 20,000 files, you’re bound to hit edge cases like missing files, corrupted DICOMs, or permission issues. Wrapping your read logic in try/except blocks will prevent your script from crashing halfway through:

from pathlib import Path
import pydicom
from pydicom.errors import InvalidDicomError

# Assume dcm_paths is your list of PosixPath objects
for idx, path in enumerate(dcm_paths):
    try:
        # First, validate the path exists and is a file
        if not path.is_file():
            print(f"Warning ({idx}/{len(dcm_paths)}): Not a valid file - {path}")
            continue
        
        # Read the DICOM file
        ds = pydicom.dcmread(str(path))
        
        # Add your processing logic here (e.g., extract metadata, pixel data)
        print(f"Success ({idx}/{len(dcm_paths)}): Read {path.name}")
    
    except PermissionError:
        print(f"Error ({idx}/{len(dcm_paths)}): Permission denied for {path}")
    except InvalidDicomError:
        print(f"Error ({idx}/{len(dcm_paths)}): {path.name} is not a valid DICOM file")
    except Exception as e:
        print(f"Unexpected error ({idx}/{len(dcm_paths)}) reading {path}: {str(e)}")

Processing 20k files can be slow if done sequentially. Here are a couple of tweaks to speed things up:

• Filter invalid paths first: Pre-process your list to only include files with .dcm suffix and valid existence:

  valid_dcm_paths = [p for p in dcm_paths if p.is_file() and p.suffix.lower() == ".dcm"]
  

• Use multiprocessing: Since reading files is IO-bound, using multiprocessing.Pool can significantly cut down on total time (just make sure your processing logic is thread-safe):

  from multiprocessing import Pool
  
  def process_dcm(path):
      try:
          ds = pydicom.dcmread(str(path))
          # Return processed data or metadata
          return (path.name, ds.PatientID)
      except Exception as e:
          return (path.name, str(e))
  
  with Pool(processes=4) as pool:
      results = pool.map(process_dcm, valid_dcm_paths)
  

Double-check that your PosixPath objects point to the right locations. Sometimes relative paths or special characters (spaces, non-ASCII) can cause issues:

# Print the first 5 paths to verify
for path in dcm_paths[:5]:
    print(f"Path: {path}")
    print(f"Absolute path: {path.absolute()}")
    print(f"Is file: {path.is_file()}\n")

If using relative paths, ensure your script’s working directory matches what you expect (you can check with Path.cwd()).

内容的提问来源于stack exchange，提问作者user9439906