How to Handle PSD Core Exceptions in Python

Aspose.PSD FOSS for Python defines two exception types: PsdLoadException, raised while parsing a PSD/PSB document, and PsdSaveException, raised while writing one. Both derive from the built-in Exception and accept a message plus an optional inner exception.

Step-by-Step Guide

Step 1: Install the Package

git clone https://github.com/aspose-psd-foss/Aspose.PSD-FOSS-for-Python.git
cd Aspose.PSD-FOSS-for-Python
# No packaging manifest is published yet -- run from this folder,
# or add it to PYTHONPATH:
export PYTHONPATH=$PWD:$PYTHONPATH

Step 2: Import Required Classes

from aspose_psd_foss.psdimage import PsdImage
from aspose_psd_foss.coreexceptions.psdloadexception import PsdLoadException
from aspose_psd_foss.coreexceptions.psdsaveexception import PsdSaveException

Step 3: Catch Load-Time Failures

PsdLoadException is raised when a document’s structure fails validation — for example, an unsupported PSD/PSB version, a section length that exceeds the enclosing section’s declared boundary, or truncated stream data:

try:
    image = PsdImage.load("input.psd")
except PsdLoadException as ex:
    print(f"Failed to load PSD/PSB file: {ex}")

Step 4: Catch Save-Time Failures

PsdSaveException is raised while writing a document — for example, when a string value exceeds the length a PSD Pascal string field can hold (255 bytes):

try:
    image.save("output.psd")
except PsdSaveException as ex:
    print(f"Failed to save PSD/PSB file: {ex}")

Step 5: Inspect an Inner Exception

Both exception types accept an inner_exception constructor argument (used internally, for example, when an I/O error interrupts reading the file structure). Check inner_exception for the underlying cause:

try:
    image = PsdImage.load("input.psd")
except PsdLoadException as ex:
    if ex.inner_exception is not None:
        print(f"Underlying I/O error: {ex.inner_exception}")

Common Issues and Fixes

PsdLoadException with a message about an unsupported version. The file’s declared PSD version field is neither the standard PSD nor the large-document PSB value. Confirm the file is a genuine, uncorrupted PSD/PSB document.

PsdLoadException with a message about a section length exceeding a boundary. The file’s internal length fields are inconsistent with its actual size — this usually indicates a truncated or corrupted file rather than an unsupported variant.

PsdSaveException about a Pascal string length. A string value (such as a layer or resource name) exceeds 255 bytes, the maximum a PSD Pascal string field can encode. Shorten the value before saving.

Frequently Asked Questions

Do PsdLoadException and PsdSaveException share a common base exception type?

No — both derive directly from the built-in Exception, not from each other or a shared Aspose.PSD base exception class.

Can PsdSaveException occur for reasons other than a long string value?

The confirmed raise site in this FOSS build is the Pascal-string-length check. Other save-time I/O failures (for example, a destination stream that cannot be written to) surface as the underlying Python exception type rather than being wrapped in PsdSaveException.

Will catching `Exception` also catch these two types?

Yes, since both derive from Exception — but catching the specific types lets you distinguish load failures from save failures.