A semicircular parliament seat chart visualizes political party representation by arranging seats in concentric arcs. Each seat is displayed as an individual dot or segment, colored by party affiliation. This visualization is ideal for showing the composition of legislative bodies, election results, and voting bloc distributions at a glance.
""" anyplot.ai
parliament-basic: Parliament Seat Chart
Library: plotly 6.7.0 | Python 3.13.13
Quality: 90/100 | Updated: 2026-05-17
"""
import os
import site
import sys
# Remove current directory from sys.path to avoid shadowing installed packages
sys.path = [p for p in sys.path if p not in ("", ".") and not p.endswith("/python")]
# Ensure site-packages are at the front
for sp in reversed(site.getsitepackages()):
sys.path.insert(0, sp)
import numpy as np
import plotly.graph_objects as go
# Theme tokens
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
GRID = "rgba(26,26,23,0.10)" if THEME == "light" else "rgba(240,239,232,0.10)"
# Okabe-Ito palette (positions 1→6, first is always #009E73)
IMPRINT = ["#009E73", "#C475FD", "#4467A3", "#BD8233", "#AE3030", "#2ABCCD"]
# Data - Fictional parliament with neutral party names
parties = [
{"name": "Progressive Alliance", "seats": 145},
{"name": "Civic Union", "seats": 118},
{"name": "Green Future", "seats": 52},
{"name": "Liberty Party", "seats": 48},
{"name": "Reform Coalition", "seats": 35},
{"name": "Independent Group", "seats": 22},
]
# Assign Okabe-Ito colors to parties
for i, party in enumerate(parties):
party["color"] = IMPRINT[i % len(IMPRINT)]
total_seats = sum(p["seats"] for p in parties)
majority_threshold = total_seats // 2 + 1
# Calculate seat positions in semicircular arrangement
n_rows = 7 if total_seats <= 500 else 9
inner_radius = 0.4
row_spacing = 0.11
# Calculate seats per row (outer rows have more seats due to larger circumference)
row_seats = []
for row in range(n_rows):
radius = inner_radius + row * row_spacing
# Seats proportional to arc length (radius)
seats_in_row = int(total_seats * radius / sum(inner_radius + i * row_spacing for i in range(n_rows)))
row_seats.append(max(seats_in_row, 1))
# Adjust to match total seats exactly
diff = total_seats - sum(row_seats)
for i in range(abs(diff)):
idx = (n_rows - 1 - i % n_rows) if diff > 0 else (i % n_rows)
row_seats[idx] += 1 if diff > 0 else -1
# Generate all seat positions sorted by angle (left to right = pi to 0)
all_seats = []
for row, n_seats in enumerate(row_seats):
radius = inner_radius + row * row_spacing
for i in range(n_seats):
# Angle from left (pi) to right (0) - seats go left to right
angle = np.pi - (i + 0.5) * np.pi / n_seats
all_seats.append({"x": radius * np.cos(angle), "y": radius * np.sin(angle), "angle": angle, "row": row})
# Sort all seats by angle (descending = left to right in parliament view)
all_seats.sort(key=lambda s: -s["angle"])
# Assign parties to seats (parties fill seats from left to right)
positions = []
seat_idx = 0
for party in parties:
for _ in range(party["seats"]):
if seat_idx < len(all_seats):
seat = all_seats[seat_idx]
positions.append(
{"x": seat["x"], "y": seat["y"], "party": party["name"], "color": party["color"], "row": seat["row"]}
)
seat_idx += 1
# Create figure
fig = go.Figure()
# Add seats grouped by party for legend
for party in parties:
party_positions = [p for p in positions if p["party"] == party["name"]]
fig.add_trace(
go.Scatter(
x=[p["x"] for p in party_positions],
y=[p["y"] for p in party_positions],
mode="markers",
marker=dict(size=14, color=party["color"], line=dict(color=PAGE_BG, width=1)),
name=f"{party['name']} ({party['seats']})",
hovertemplate=f"{party['name']}<br>Seats: {party['seats']}<extra></extra>",
)
)
# Add majority threshold arc (more visible with increased alpha)
threshold_angle = np.linspace(0, np.pi, 100)
threshold_radius = 0.5 + 0.12 * (len(set(p["row"] for p in positions)) / 2)
fig.add_trace(
go.Scatter(
x=threshold_radius * np.cos(threshold_angle),
y=threshold_radius * np.sin(threshold_angle),
mode="lines",
line=dict(color=INK_SOFT, width=3, dash="dash"),
name=f"Majority ({majority_threshold})",
hoverinfo="skip",
)
)
# Layout
fig.update_layout(
title=dict(text="parliament-basic · plotly · anyplot.ai", font=dict(size=28, color=INK), x=0.5, xanchor="center"),
xaxis=dict(showgrid=False, zeroline=False, showticklabels=False, range=[-1.3, 1.3], scaleanchor="y", scaleratio=1),
yaxis=dict(showgrid=False, zeroline=False, showticklabels=False, range=[-0.15, 1.2]),
legend=dict(
orientation="h",
yanchor="bottom",
y=-0.15,
xanchor="center",
x=0.5,
font=dict(size=16, color=INK_SOFT),
bgcolor=ELEVATED_BG,
bordercolor=INK_SOFT,
borderwidth=1,
itemsizing="constant",
),
paper_bgcolor=PAGE_BG,
plot_bgcolor=PAGE_BG,
margin=dict(l=50, r=50, t=100, b=120),
)
# Add annotation for total seats
fig.add_annotation(
x=0, y=0.05, text=f"<b>{total_seats}</b><br>seats", font=dict(size=24, color=INK), showarrow=False, align="center"
)
# Save outputs
fig.write_image(f"plot-{THEME}.png", width=1600, height=900, scale=3)
fig.write_html(f"plot-{THEME}.html", include_plotlyjs="cdn")
Part of Parliament Seat Chart on anyplot.ai.