Plotext Financial Chart Skill

Create ASCII financial line charts for GitHub Flavored Markdown using plotext with dot marker (•). Pure text output — renders correctly on GitHub, terminals, and all monospace environments.

Analogy: graph-easy is for flowcharts. plotext with dot marker is for financial line charts.

When to Use This Skill

Adding price path / line chart diagrams to markdown documentation
Visualizing trading concepts (barriers, thresholds, entry/exit levels)
Any GFM markdown file needing financial data visualization
User mentions "financial chart", "line chart", "price chart", "plotext", or "trading chart"

NOT for: Flowcharts or architecture diagrams — use graph-easy for those.

Preflight Check

All-in-One Preflight Script

/usr/bin/env bash << 'PREFLIGHT_EOF'
python3 --version &>/dev/null || { echo "ERROR: Python 3 not found"; exit 1; }
if command -v uv &>/dev/null; then PM="uv pip"
elif command -v pip3 &>/dev/null; then PM="pip3"
else echo "ERROR: Neither uv nor pip3 found"; exit 1; fi
python3 -c "import plotext" 2>/dev/null || { echo "Installing plotext via $PM..."; $PM install plotext; }
python3 -c "
import plotext as plt, re
plt.clear_figure()
plt.plot([1,2,3], [1,2,3], marker='dot')
plt.plotsize(20, 5)
plt.theme('clear')
output = re.sub(r'\x1b\[[0-9;]*m', '', plt.build())
assert '•' in output
" && echo "✓ plotext ready (dot marker verified)"
PREFLIGHT_EOF

Quick Start

import re
import plotext as plt

x = list(range(20))
y = [97, 98, 100, 101, 100, 98, 100, 101, 102, 101,
     100, 98, 100, 101, 102, 103, 102, 101, 100, 100]

plt.clear_figure()
plt.plot(x, y, marker="dot", label="Price path")
plt.hline(103)    # Upper barrier
plt.hline(97)     # Lower barrier
plt.hline(100)    # Entry price
plt.title("Triple Barrier Method")
plt.xlabel("Time (bars)")
plt.ylabel("Price")
plt.plotsize(65, 22)
plt.theme("clear")
print(re.sub(r'\x1b\[[0-9;]*m', '', plt.build()))

Mandatory Settings

Every chart MUST use these settings:

Setting	Code	Why
Reset state	`plt.clear_figure()`	Prevent stale data
Dot marker	`marker="dot"`	GitHub-safe alignment
No color	`plt.theme("clear")`	Clean text output
Strip ANSI	`re.sub(r'\x1b\[…', '', …)`	Remove residual escape codes
Build as string	`plt.build()`	Not `plt.show()`

Marker Reference

Marker	GitHub Safe	Use When
`"dot"`	Yes	Default — always use
`"hd"`	Yes	Terminal-only, need smoothness
`"braille"`	No	Never for markdown
`"fhd"`	No	Never — Unicode 13.0+ only

Rendering Command

/usr/bin/env bash << 'RENDER_EOF'
python3 << 'CHART_EOF'
import re
import plotext as plt

x = list(range(20))
y = [97, 98, 100, 101, 100, 98, 100, 101, 102, 101,
     100, 98, 100, 101, 102, 103, 102, 101, 100, 100]

plt.clear_figure()
plt.plot(x, y, marker="dot", label="Price path")
plt.hline(103)
plt.hline(97)
plt.hline(100)
plt.title("Triple Barrier Method")
plt.xlabel("Time (bars)")
plt.ylabel("Price")
plt.plotsize(65, 22)
plt.theme("clear")
print(re.sub(r'\x1b\[[0-9;]*m', '', plt.build()))
CHART_EOF
RENDER_EOF

Embedding in Markdown (MANDATORY: Source Adjacent to Chart)

Every chart MUST be immediately followed by a <details> block with Python source. Explanatory text goes after the <details> block, never between chart and source.

✅ CORRECT: Chart → <details> → Explanatory text
❌ WRONG:   Chart → Explanatory text → <details>

See ./references/api-and-patterns.md for full embedding template.

Mandatory Checklist

plt.clear_figure() — Reset state
marker="dot" — Dot marker for GitHub
plt.theme("clear") + re.sub() strip — No ANSI codes
plt.title("...") — Every chart needs a title
plt.xlabel / plt.ylabel — Axis labels
plt.plotsize(65, 22) — Fits 80-col code blocks
<details> block immediately after chart (before any explanatory text)

Troubleshooting

Issue	Cause	Solution
ANSI codes in output	Missing theme/strip	Add `plt.theme("clear")` and `re.sub()` strip
Misaligned on GitHub	Wrong marker type	Use `marker="dot"`, never braille/fhd
Chart too wide	plotsize too large	Use `plt.plotsize(65, 22)` for 80-col blocks
No diagonal slopes	Too few data points	Use 15+ data points for visible slopes
`ModuleNotFoundError`	Not installed	Run preflight check
Empty output	Missing `build()`	Use `plt.build()` not `plt.show()`

plotext-financial-chart