Exceptions, Warnings, and Log messages

pypdf makes use of three mechanisms to show if something went wrong:

  • Exceptions are error cases that pypdf users should explicitly handle. In the strict=True mode, most log messages with the warning level will become exceptions. This can be useful in applications where you can require a user to fix the broken PDF.

  • Warnings are avoidable issues, such as using deprecated classes / functions / parameters. Another example is missing capabilities of pypdf. In those cases, pypdf users should adjust their code. Warnings are issued by the warnings module - those are different from the log-level “warning”.

  • Log messages are informative messages that can be used for post-mortem analysis. Most of the time, users can ignore them. They come in different levels, such as info / warning / error indicating the severity. Examples are non-standard compliant PDF files which pypdf can deal with or a missing implementation that leads to a part of the text not being extracted.

Exceptions

Exceptions need to be caught if you want to handle them. For example, you could want to read the text from a PDF as a part of a search function.

Most PDF files do not follow the specification. In this case pypdf needs to guess which kinds of mistakes were potentially done when the PDF file was created. See the robustness page for the related issues.

As a user, you likely do not care about it. If it is readable in any way, you want the text. You might use pdfminer.six as a fallback and do this:

from pypdf import PdfReader
from pdfminer.high_level import extract_text as fallback_text_extraction

text = ""
try:
    reader = PdfReader("example.pdf")
    for page in reader.pages:
        text += page.extract_text()
except Exception as exc:
    text = fallback_text_extraction("example.pdf")

You could also capture pypdf.errors.PyPdfError if you prefer something more specific.

Warnings

The warnings module allows you to ignore warnings:

import warnings

warnings.filterwarnings("ignore")

In many cases, you actually want to start Python with the -W flag so that you see all warnings. This is especially true for Continuous Integration (CI).

Log messages

Log messages can be noisy in some cases. pypdf hopefully has a reasonable level of log messages, but you can reduce which types of messages you want to see:

import logging

logger = logging.getLogger("pypdf")
logger.setLevel(logging.ERROR)

The logging module defines six log levels:

  • CRITICAL

  • ERROR

  • WARNING

  • INFO

  • DEBUG

  • NOTSET