refactor: move imports to function level for lazy loading

Move module imports inside functions to defer loading until needed. This improves startup performance by reducing initial import overhead.

Author: bowenliang123

md_exporter/services/svc_md_to_html.py

@@ -6,8 +6,6 @@
 
 from pathlib import Path
 
-from pypandoc import convert_text
-
 from ..utils.markdown_utils import get_md_text
 
 
@@ -24,6 +22,8 @@ def convert_md_to_html(md_text: str, output_path: Path, is_strip_wrapper: bool =
         ValueError: If input processing fails
         Exception: If conversion fails
     """
+    from pypandoc import convert_text  # noqa: PLC0415
+
     # Process Markdown text
     processed_md = get_md_text(md_text, is_strip_wrapper=is_strip_wrapper)
 

md_exporter/services/svc_md_to_pdf.py

@@ -6,8 +6,6 @@
 
 from pathlib import Path
 
-from xhtml2pdf import pisa
-
 from ..utils.markdown_utils import convert_markdown_to_html, get_md_text
 from ..utils.text_utils import contains_chinese, contains_japanese
 
@@ -65,6 +63,8 @@ def convert_md_to_pdf(md_text: str, output_path: Path, is_strip_wrapper: bool =
         ValueError: If input processing fails
         Exception: If conversion fails
     """
+    from xhtml2pdf import pisa  # noqa: PLC0415
+
     # Process Markdown text
     processed_md = get_md_text(md_text, is_strip_wrapper=is_strip_wrapper)
 

md_exporter/services/svc_md_to_png.py

@@ -8,10 +8,6 @@
 from pathlib import Path
 from tempfile import NamedTemporaryFile
 
-import pymupdf
-from PIL import Image
-from xhtml2pdf import pisa
-
 from ..utils.logger_utils import get_logger
 from ..utils.markdown_utils import convert_markdown_to_html, get_md_text
 from ..utils.text_utils import contains_chinese, contains_japanese
@@ -68,6 +64,10 @@ def convert_md_to_png(
         ValueError: If input processing fails
         Exception: If conversion fails
     """
+    import pymupdf  # noqa: PLC0415
+    from PIL import Image  # noqa: PLC0415
+    from xhtml2pdf import pisa  # noqa: PLC0415
+
     # Process Markdown text
     processed_md = get_md_text(md_text, is_strip_wrapper=is_strip_wrapper)
 

md_exporter/utils/pandoc_utils.py

@@ -6,8 +6,6 @@
 import os
 import tempfile
 
-from pypandoc import convert_file
-
 from md_exporter.utils import get_logger
 
 DEFAULT_ENABLED_INPUT_EXTENSIONS = []
@@ -31,6 +29,8 @@ def pandoc_convert_file(
     """
     Convert file using pandoc
     """
+    from pypandoc import convert_file  # noqa: PLC0415
+
     extra_args = extra_args or []
     enabled = enabled_input_extensions or []
     disabled = disabled_input_extensions or []