NetworkDiagram

A lightweight Python library for creating Project Network Diagrams (CPM/PERT), calculating paths, and visualizing activity dependencies using NetworkX and Matplotlib.

Features

• Easy Node Management: Add activities with durations and string-based predecessor lists (e.g., "A,B").
• Automatic Pathfinding: Detects all probable paths from Start to End.
• CPM Ready: Built on a node structure supporting All Paths, Critical Path, and ES/EF/LS/LF attributes.
• Forward & Backward Pass: Automatically calculates Early Start (ES), Early Finish (EF), Late Start (LS), and Late Finish (LF) for all nodes.
• Visualization: Generates directed graphs with arrows and duration labels using matplotlib.

Publisher

• Name: Kathan Majithia
• Contact: kathanmajithia@gmail.com

Dependencies

To use the visualization features, you must have the following libraries installed:

• networkx
• matplotlib

Installation

You can install the package directly via pip:

pip install networkdiagram

Quick Start Guide

Here is a complete example of how to use the networkdiagram library to build a Critical Path Method (CPM) diagram, calculate properties, and visualize the output.

from networkdiagram import CriticalPathMethod

# 1. Initialize the CPM Network
cpm = CriticalPathMethod()

# 2. Define Activities
activities = ['A', 'B', 'C', 'D']
durations = [2, 5, 4, 2]
predecessors = ['-', 'A', 'B', 'B,C']

# 3. Add Origin and Activities to the Network
cpm.add_activity('O', 0)
cpm.add_activities_relations(activities, durations, predecessors)

# 4. Perform Path Calculations
cpm.find_probable_paths()
cpm.find_critical_path()

# 5. Calculate Early & Late Start/Finish
cpm.forward_pass()
cpm.backward_pass()

# 6. Generate Network Summary
cpm.network_summary()

# 7. Visualize the Network
cpm.get_edges()
cpm.display_network()

CPM Calculation Workflow

The following workflow illustrates how NetworkDiagram processes activities and computes CPM metrics.

flowchart TD
    A[Define Activities] --> B[Create Network]
    B --> C[Add Dependencies]
    C --> D[Find Probable Paths]
    D --> E[Find Critical Path]
    E --> F[Forward Pass]
    F --> G[Backward Pass]
    G --> H[Generate Network Summary]
    H --> I[Display Network]

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Forward Pass Calculation

The Forward Pass calculates the earliest possible start and finish times for each activity in the network.

Formula

ES = Maximum EF of predecessor activities
EF = ES + Duration

Visual Example

flowchart LR
    A["Activity A<br/>ES = 0<br/>EF = 3"]
    B["Activity B<br/>ES = 3<br/>EF = 5"]
    C["Activity C<br/>ES = 5<br/>EF = 9"]

    A --> B --> C

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Backward Pass Calculation

The Backward Pass calculates the latest possible start and finish times without delaying the project.

Formula

LF = Minimum LS of successor activities
LS = LF - Duration

Visual Example

flowchart RL
    C["Activity C<br/>LS = 5<br/>LF = 9"]
    B["Activity B<br/>LS = 3<br/>LF = 5"]
    A["Activity A<br/>LS = 0<br/>LF = 3"]

    C --> B --> A

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Example Network Diagram

Example network diagram generated using NetworkDiagram.

Network Summary

Network summary generated after performing CPM calculations.

Practical Examples

Example 1: Simple Project Network

The Quick Start Guide demonstrates a simple CPM network consisting of a few activities and dependencies.

Expected Output

• Generates a project network diagram.
• Identifies the critical path.
• Computes Early Start (ES) and Early Finish (EF).
• Computes Late Start (LS) and Late Finish (LF).
• Produces a network summary.

Example 2: Intermediate Project Network

Suitable for projects with multiple dependencies and branching paths.

Expected Output

• Handles multiple activity dependencies.
• Identifies the critical path.
• Computes CPM metrics.
• Generates a visual project network.

Example 3: Complex Project Network

Suitable for larger project schedules with several parallel paths.

Expected Output

• Supports larger project structures.
• Displays multiple probable paths.
• Highlights the critical path.
• Provides complete scheduling analysis.

Accessing Node Properties

After running the forward and backward passes, each activity node will have its CPM properties populated. You can access these programmatically:

node_a = cpm.nodes['A']

print(f"ES: {node_a.early_start}, EF: {node_a.early_finish}")
print(f"LS: {node_a.latest_start}, LF: {node_a.latest_finish}")

Contributing

We welcome contributions!

1. Please read our CONTRIBUTING.md for detailed guidelines.
2. Ensure you are assigned to an issue before submitting a Pull Request.
3. PRs must be submitted against the main branch.
4. If modifying mathematical logic, please ensure you verify your algorithms against known project networks.

👥 Contributors

Thanks to all contributors ❤️

License

This project is licensed under the MIT License.