Fix excess whitespace in streaming output from code cells

.github/copilot-instructions.md

@@ -80,9 +80,10 @@ src/quantecon_book_theme/
 - **Regression tests**: Tests compare generated HTML against golden files in `tests/test_build/`
 
 ### Code Quality Workflow
-- Always run `pre-commit run --all-files` before committing
+- **CRITICAL**: ALWAYS run `pre-commit run --all-files` before committing to GitHub
 - Pre-commit includes: black (formatting), flake8 (linting), YAML/JSON validation
 - CI will fail if pre-commit checks don't pass
+- If you make changes to Python or SCSS files, run pre-commit before `git commit`
 
 ## Troubleshooting
 
@@ -116,10 +117,13 @@ pre-commit install
 # Development workflow
 npm run build                    # Compile assets (2.5-3 seconds, VALIDATED)
 tox -e docs-live                # Live development server (5-10 minutes)
-pre-commit run --all-files      # Code quality checks (2-5 minutes, VALIDATED)
+pre-commit run --all-files      # Code quality checks (2-5 minutes, VALIDATED) - RUN BEFORE COMMITTING
 flake8 src/                     # Python linting (few seconds, VALIDATED)
 black --check src/              # Formatting check (few seconds, VALIDATED)
 
+# Before committing to GitHub
+pre-commit run --all-files      # CRITICAL: Always run before git commit
+
 # Testing and CI
 tox                             # Full test suite (5-15 minutes)
 tox -e docs-update              # Build documentation (5-15 minutes)

src/quantecon_book_theme/assets/styles/index.scss

@@ -298,6 +298,27 @@ body {
   }
 }
 
+// Fix excess spacing in streaming output (Issue #325)
+// Remove all spacing between consecutive streaming outputs
+.cell_output .output.stream + .output.stream {
+  margin-top: 0 !important;
+}
+
+// Remove internal spacing from all streaming output elements
+.cell_output .output.stream {
+  .highlight {
+    margin-top: 0 !important;
+    margin-bottom: 0 !important;
+
+    // Remove margin and padding from pre elements
+    pre {
+      margin: 0 !important;
+      padding-top: 0 !important;
+      padding-bottom: 0 !important;
+    }
+  }
+}
+
 .section,
 .reference,
 .math {

tests/sites/base/section1/index.md

@@ -3,6 +3,7 @@
 ```{toctree}
 page1
 ntbk
+ntbk_streaming
 ntbkmd
 ntbk_octave
 ntbk_julia

tests/sites/base/section1/ntbk_streaming.ipynb

@@ -0,0 +1,117 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Test Streaming Output\n",
+    "\n",
+    "This notebook tests streaming output from multiple print statements."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Error at iteration 25 is 40.0.\n"
+     ]
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Error at iteration 50 is 20.0.\n"
+     ]
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Error at iteration 75 is 13.333333333333334.\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Test with streaming output from loop\n",
+    "# Each print statement creates a separate stream output\n",
+    "for i in [25, 50, 75]:\n",
+    "    error = 100 / (i / 10)\n",
+    "    print(f\"Error at iteration {i} is {error}.\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Line 1\n"
+     ]
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Line 2\n"
+     ]
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Line 3\n"
+     ]
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Line 4\n"
+     ]
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Line 5\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Test with multiple consecutive print statements\n",
+    "# Each creates a separate stream output\n",
+    "for i in range(1, 6):\n",
+    "    print(f\"Line {i}\")"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.0"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}

tests/test_build.py

@@ -422,3 +422,49 @@ def test_qetheme_code_style(sphinx_build):
     # String "true" should be treated as True
     assert "use-pygments-style" not in body_tag.get("class", [])
     sphinx_build.clean()
+
+
+def test_streaming_output_spacing(sphinx_build):
+    """Test that streaming output structure supports CSS spacing fix.
+
+    This test verifies the fix for issue #325 where consecutive stream outputs
+    have comprehensive CSS applied to remove excessive spacing.
+    """
+    sphinx_build.copy()
+    sphinx_build.build()
+
+    # Get the streaming output notebook page
+    streaming_html = sphinx_build.get("section1/ntbk_streaming.html")
+
+    # Find all stream output divs
+    stream_outputs = streaming_html.find_all("div", class_="output")
+    stream_divs = [div for div in stream_outputs if "stream" in div.get("class", [])]
+
+    # Should have multiple stream outputs from the test notebook
+    assert (
+        len(stream_divs) >= 8
+    ), f"Should have at least 8 streaming output elements, found {len(stream_divs)}"
+
+    # Verify we have consecutive streaming outputs (adjacent siblings)
+    cell_outputs = streaming_html.find_all("div", class_="cell_output")
+    assert len(cell_outputs) >= 2, "Should have at least 2 cells with outputs"
+
+    # At least one cell should have consecutive stream outputs for CSS to target
+    found_consecutive = False
+    for cell_output in cell_outputs:
+        stream_children = [
+            child
+            for child in cell_output.children
+            if child.name == "div"
+            and "output" in child.get("class", [])
+            and "stream" in child.get("class", [])
+        ]
+        if len(stream_children) >= 2:
+            found_consecutive = True
+            break
+
+    assert (
+        found_consecutive
+    ), "Should have consecutive stream outputs for CSS fix to apply"
+
+    sphinx_build.clean()

tests/test_build/test_build_book.html

@@ -41,19 +41,24 @@
         3.2. A test notebook
        </a>
       </li>
+      <li class="toctree-l2">
+       <a class="reference internal" href="section1/ntbk_streaming.html">
+        3.3. Test Streaming Output
+       </a>
+      </li>
       <li class="toctree-l2">
        <a class="reference internal" href="section1/ntbkmd.html">
-        3.3. Section 1 page1
+        3.4. Section 1 page1
        </a>
       </li>
       <li class="toctree-l2">
        <a class="reference internal" href="section1/ntbk_octave.html">
-        3.4. Octave
+        3.5. Octave
        </a>
       </li>
       <li class="toctree-l2">
        <a class="reference internal" href="section1/ntbk_julia.html">
-        3.5. Julia
+        3.6. Julia
        </a>
       </li>
      </ul>