A Gantt chart that visualizes project schedules with task dependencies and groupings. Beyond displaying task timelines, this chart shows relationships between tasks using connector arrows, indicating which tasks must complete before others can begin. Tasks can be organized into groups (phases or work packages) with aggregate timeline bars showing the span of each group. This visualization is essential for understanding critical paths and scheduling constraints in complex projects.
""" anyplot.ai
gantt-dependencies: Gantt Chart with Dependencies
Library: plotnine 0.15.4 | Python 3.13.13
Quality: 91/100 | Updated: 2026-06-02
"""
import os
from datetime import datetime, timedelta
import pandas as pd
from plotnine import (
aes,
element_blank,
element_line,
element_rect,
element_text,
geom_point,
geom_rect,
geom_segment,
ggplot,
labs,
scale_fill_manual,
scale_x_datetime,
scale_y_continuous,
theme,
theme_minimal,
)
# Theme tokens — Imprint palette, theme-adaptive chrome
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"
# Imprint palette — 4 project phases (canonical order, positions 1–4)
group_colors = {"Requirements": "#009E73", "Design": "#C475FD", "Development": "#4467A3", "Testing": "#BD8233"}
# Data: software development project with finish-to-start dependencies
tasks_data = [
{
"task": "Gather Requirements",
"start": datetime(2024, 1, 1),
"end": datetime(2024, 1, 10),
"group": "Requirements",
"depends_on": [],
},
{
"task": "Document Specs",
"start": datetime(2024, 1, 10),
"end": datetime(2024, 1, 17),
"group": "Requirements",
"depends_on": ["Gather Requirements"],
},
{
"task": "Review & Approve",
"start": datetime(2024, 1, 17),
"end": datetime(2024, 1, 20),
"group": "Requirements",
"depends_on": ["Document Specs"],
},
{
"task": "System Architecture",
"start": datetime(2024, 1, 20),
"end": datetime(2024, 1, 30),
"group": "Design",
"depends_on": ["Review & Approve"],
},
{
"task": "Database Design",
"start": datetime(2024, 1, 30),
"end": datetime(2024, 2, 7),
"group": "Design",
"depends_on": ["System Architecture"],
},
{
"task": "UI/UX Mockups",
"start": datetime(2024, 1, 20),
"end": datetime(2024, 2, 3),
"group": "Design",
"depends_on": ["Review & Approve"],
},
{
"task": "Backend API",
"start": datetime(2024, 2, 7),
"end": datetime(2024, 2, 28),
"group": "Development",
"depends_on": ["Database Design"],
},
{
"task": "Frontend Components",
"start": datetime(2024, 2, 3),
"end": datetime(2024, 2, 25),
"group": "Development",
"depends_on": ["UI/UX Mockups"],
},
{
"task": "Integration",
"start": datetime(2024, 2, 28),
"end": datetime(2024, 3, 8),
"group": "Development",
"depends_on": ["Backend API", "Frontend Components"],
},
{
"task": "Unit Testing",
"start": datetime(2024, 2, 28),
"end": datetime(2024, 3, 8),
"group": "Testing",
"depends_on": ["Backend API"],
},
{
"task": "Integration Testing",
"start": datetime(2024, 3, 8),
"end": datetime(2024, 3, 15),
"group": "Testing",
"depends_on": ["Integration"],
},
{
"task": "User Acceptance",
"start": datetime(2024, 3, 15),
"end": datetime(2024, 3, 21),
"group": "Testing",
"depends_on": ["Integration Testing"],
},
]
df = pd.DataFrame(tasks_data)
# Critical path: longest finish-to-start chain through the project
critical_path_tasks = {
"Gather Requirements",
"Document Specs",
"Review & Approve",
"System Architecture",
"Database Design",
"Backend API",
"Integration",
"Integration Testing",
"User Acceptance",
}
# Build y-axis positions — group header above each group's tasks
group_order = ["Requirements", "Design", "Development", "Testing"]
task_labels = {}
y_pos = 0
group_positions = {}
task_positions = {}
for grp in group_order:
group_positions[grp] = y_pos
task_labels[y_pos] = f"▸ {grp}"
y_pos += 1
for _, row in df[df["group"] == grp].iterrows():
task_positions[row["task"]] = y_pos
task_labels[y_pos] = f" {row['task']}"
y_pos += 1
# Group aggregate bars spanning each group's full date range
group_data = [
{
"y": group_positions[grp],
"start": df[df["group"] == grp]["start"].min(),
"end": df[df["group"] == grp]["end"].max(),
"group": grp,
"ymin": group_positions[grp] - 0.42,
"ymax": group_positions[grp] + 0.42,
}
for grp in group_order
]
# Task bars split by critical path membership (geom_rect requires ymin/ymax)
critical_task_data = []
normal_task_data = []
for _, row in df.iterrows():
y = task_positions[row["task"]]
hw = 0.34 if row["task"] in critical_path_tasks else 0.26
entry = {"y": y, "start": row["start"], "end": row["end"], "group": row["group"], "ymin": y - hw, "ymax": y + hw}
(critical_task_data if row["task"] in critical_path_tasks else normal_task_data).append(entry)
phase_order = pd.CategoricalDtype(categories=group_order, ordered=True)
groups_df = pd.DataFrame(group_data)
groups_df["group"] = groups_df["group"].astype(phase_order)
critical_df = pd.DataFrame(critical_task_data)
critical_df["group"] = critical_df["group"].astype(phase_order)
normal_df = pd.DataFrame(normal_task_data)
normal_df["group"] = normal_df["group"].astype(phase_order)
# L-shaped dependency connectors: vertical leg + horizontal leg + V-arrowhead
arrow_size_days = 1.8
arrow_wing = 0.22
vert_segs = []
horiz_segs = []
arrowhead_segs = []
for _, row in df.iterrows():
for dep_name in row["depends_on"]:
if dep_name not in task_positions:
continue
dep_row = df[df["task"] == dep_name].iloc[0]
x_bend = dep_row["end"]
x_target = row["start"]
y_dep = task_positions[dep_name]
y_task = task_positions[row["task"]]
is_crit = dep_name in critical_path_tasks and row["task"] in critical_path_tasks
vert_segs.append({"x_start": x_bend, "x_end": x_bend, "y_start": y_dep, "y_end": y_task, "critical": is_crit})
horiz_segs.append(
{
"x_start": x_bend,
"x_end": x_target - timedelta(days=arrow_size_days * 0.3),
"y_start": y_task,
"y_end": y_task,
"critical": is_crit,
}
)
# V-arrowhead: two lines converging at x_target
arrowhead_segs.append(
{
"x_start": x_target - timedelta(days=arrow_size_days),
"x_end": x_target,
"y_start": y_task - arrow_wing,
"y_end": y_task,
"critical": is_crit,
}
)
arrowhead_segs.append(
{
"x_start": x_target - timedelta(days=arrow_size_days),
"x_end": x_target,
"y_start": y_task + arrow_wing,
"y_end": y_task,
"critical": is_crit,
}
)
vert_df = pd.DataFrame(vert_segs)
horiz_df = pd.DataFrame(horiz_segs)
arrowhead_df = pd.DataFrame(arrowhead_segs)
crit_vert = vert_df[vert_df["critical"]]
norm_vert = vert_df[~vert_df["critical"]]
crit_horiz = horiz_df[horiz_df["critical"]]
norm_horiz = horiz_df[~horiz_df["critical"]]
crit_heads = arrowhead_df[arrowhead_df["critical"]]
norm_heads = arrowhead_df[~arrowhead_df["critical"]]
# Milestone diamonds at key phase-handoff points
milestones = pd.DataFrame(
[
{"x": datetime(2024, 1, 20), "y": task_positions["Review & Approve"]},
{"x": datetime(2024, 2, 7), "y": task_positions["Database Design"]},
{"x": datetime(2024, 2, 28), "y": task_positions["Backend API"]},
{"x": datetime(2024, 3, 21), "y": task_positions["User Acceptance"]},
]
)
y_breaks = list(task_labels.keys())
y_labels_list = [task_labels[y] for y in y_breaks]
title = "gantt-dependencies · python · plotnine · anyplot.ai"
n = len(title)
title_fontsize = max(round(12 * 67 / n) if n > 67 else 12, 8)
plot = (
ggplot()
# Non-critical task bars (subdued)
+ geom_rect(
data=normal_df,
mapping=aes(xmin="start", xmax="end", ymin="ymin", ymax="ymax", fill="group"),
color=None,
alpha=0.5,
)
# Critical path task bars (prominent, slightly taller)
+ geom_rect(
data=critical_df,
mapping=aes(xmin="start", xmax="end", ymin="ymin", ymax="ymax", fill="group"),
color=None,
alpha=1.0,
)
# Group aggregate bars (tallest — span each phase)
+ geom_rect(
data=groups_df,
mapping=aes(xmin="start", xmax="end", ymin="ymin", ymax="ymax", fill="group"),
color=None,
alpha=0.85,
)
# Non-critical connectors
+ geom_segment(
data=norm_vert,
mapping=aes(x="x_start", xend="x_end", y="y_start", yend="y_end"),
color=INK_SOFT,
size=0.4,
alpha=0.7,
)
+ geom_segment(
data=norm_horiz,
mapping=aes(x="x_start", xend="x_end", y="y_start", yend="y_end"),
color=INK_SOFT,
size=0.4,
alpha=0.7,
)
+ geom_segment(
data=norm_heads,
mapping=aes(x="x_start", xend="x_end", y="y_start", yend="y_end"),
color=INK_SOFT,
size=0.6,
alpha=0.75,
)
# Critical path connectors (bolder, theme-ink color)
+ geom_segment(
data=crit_vert,
mapping=aes(x="x_start", xend="x_end", y="y_start", yend="y_end"),
color=INK,
size=0.6,
alpha=0.9,
)
+ geom_segment(
data=crit_horiz,
mapping=aes(x="x_start", xend="x_end", y="y_start", yend="y_end"),
color=INK,
size=0.6,
alpha=0.9,
)
+ geom_segment(
data=crit_heads,
mapping=aes(x="x_start", xend="x_end", y="y_start", yend="y_end"),
color=INK,
size=0.9,
alpha=0.95,
)
# Milestone diamonds at phase-handoff points
+ geom_point(
data=milestones, mapping=aes(x="x", y="y"), shape="D", size=2, color="#AE3030", fill="#AE3030", alpha=0.9
)
# Scales
+ scale_fill_manual(values=group_colors, name="Project Phase", limits=group_order)
+ scale_y_continuous(breaks=y_breaks, labels=y_labels_list, trans="reverse")
+ scale_x_datetime(
date_breaks="1 week", date_labels="%b %d", limits=(datetime(2023, 12, 29), datetime(2024, 3, 22))
)
# Labels
+ labs(
title=title,
subtitle="Bold bars & dark arrows = Critical Path | Subdued bars & muted arrows = Non-critical",
x="Date (2024)",
y="",
)
# Theme — Imprint palette chrome, theme-adaptive backgrounds and text
+ theme_minimal()
+ theme(
figure_size=(8, 4.5),
plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
panel_background=element_rect(fill=PAGE_BG),
plot_title=element_text(size=title_fontsize, weight="bold", color=INK, margin={"b": 3}),
plot_subtitle=element_text(size=8, color=INK_SOFT, margin={"b": 5}),
axis_title_x=element_text(size=10, color=INK),
axis_text_x=element_text(size=8, color=INK_SOFT, rotation=45, ha="right"),
axis_text_y=element_text(size=8, color=INK_SOFT, ha="right"),
legend_title=element_text(size=8, weight="bold", color=INK),
legend_text=element_text(size=8, color=INK_SOFT),
legend_position="right",
legend_background=element_rect(fill=ELEVATED_BG, color=INK_SOFT),
legend_key_size=8,
panel_grid_major_y=element_blank(),
panel_grid_minor=element_blank(),
panel_grid_major_x=element_line(color=INK, size=0.2, alpha=0.15),
panel_border=element_rect(color=INK_SOFT, fill=None),
axis_line=element_line(color=INK_SOFT),
)
)
plot.save(f"plot-{THEME}.png", dpi=400, width=8, height=4.5, units="in", verbose=False)
Part of Gantt Chart with Dependencies on anyplot.ai.