change-order-processor（变更单处理器）

Change Order Processor

Business Case

Problem Statement

Change orders cause project disruption:

• Delayed processing affects cash flow
• Unclear cost impact
• Lost documentation
• Schedule impacts not tracked

Solution

Streamlined change order processing with cost analysis, approval workflow, and impact tracking.

Business Value

• Faster processing - Reduce approval cycle time
• Cost control - Accurate change pricing
• Documentation - Complete audit trail
• Impact visibility - Schedule and budget effects

Technical Implementation

import pandas as pd
from datetime import datetime, date, timedelta
from typing import Dict, Any, List, Optional
from dataclasses import dataclass, field
from enum import Enum

class ChangeOrderStatus(Enum):
    """Change order status."""
    DRAFT = "draft"
    PENDING_REVIEW = "pending_review"
    PENDING_APPROVAL = "pending_approval"
    APPROVED = "approved"
    REJECTED = "rejected"
    VOID = "void"

class ChangeType(Enum):
    """Type of change."""
    OWNER_REQUESTED = "owner_requested"
    DESIGN_CHANGE = "design_change"
    FIELD_CONDITION = "field_condition"
    CODE_COMPLIANCE = "code_compliance"
    VALUE_ENGINEERING = "value_engineering"
    ERROR_OMISSION = "error_omission"

class ImpactType(Enum):
    """Impact categories."""
    COST_INCREASE = "cost_increase"
    COST_DECREASE = "cost_decrease"
    TIME_INCREASE = "time_increase"
    TIME_DECREASE = "time_decrease"
    NO_IMPACT = "no_impact"

@dataclass
class CostItem:
    """Change order cost item."""
    description: str
    quantity: float
    unit: str
    unit_cost: float
    total_cost: float
    category: str  # labor, material, equipment, subcontractor
    markup_percent: float = 0.0

@dataclass
class ApprovalRecord:
    """Approval workflow record."""
    approver_name: str
    approver_role: str
    action: str  # approved, rejected, returned
    action_date: datetime
    comments: str = ""

@dataclass
class ChangeOrder:
    """Change order record."""
    co_number: str
    title: str
    description: str
    change_type: ChangeType
    status: ChangeOrderStatus
    created_date: date
    created_by: str

    # Cost
    cost_items: List[CostItem] = field(default_factory=list)
    direct_cost: float = 0.0
    overhead_cost: float = 0.0
    profit_cost: float = 0.0
    total_cost: float = 0.0

    # Schedule
    schedule_impact_days: int = 0
    affected_activities: List[str] = field(default_factory=list)

    # Workflow
    approvals: List[ApprovalRecord] = field(default_factory=list)
    approved_date: Optional[date] = None
    approved_by: str = ""

    # References
    rfi_reference: str = ""
    spec_section: str = ""
    drawing_reference: str = ""
    location: str = ""

    def to_dict(self) -> Dict[str, Any]:
        return {
            'co_number': self.co_number,
            'title': self.title,
            'change_type': self.change_type.value,
            'status': self.status.value,
            'created_date': self.created_date.isoformat(),
            'direct_cost': self.direct_cost,
            'overhead_cost': self.overhead_cost,
            'profit_cost': self.profit_cost,
            'total_cost': self.total_cost,
            'schedule_impact': self.schedule_impact_days,
            'approved_date': self.approved_date.isoformat() if self.approved_date else None
        }

class ChangeOrderProcessor:
    """Process and manage change orders."""

    DEFAULT_OVERHEAD_RATE = 0.10
    DEFAULT_PROFIT_RATE = 0.10

    def __init__(self, project_name: str, original_contract: float,
                 overhead_rate: float = None, profit_rate: float = None):
        self.project_name = project_name
        self.original_contract = original_contract
        self.overhead_rate = overhead_rate or self.DEFAULT_OVERHEAD_RATE
        self.profit_rate = profit_rate or self.DEFAULT_PROFIT_RATE
        self.change_orders: Dict[str, ChangeOrder] = {}
        self._co_counter = 0

    def create_change_order(self,
                           title: str,
                           description: str,
                           change_type: ChangeType,
                           created_by: str,
                           rfi_reference: str = "",
                           location: str = "") -> ChangeOrder:
        """Create new change order."""
        self._co_counter += 1
        co_number = f"CO-{self._co_counter:04d}"

        co = ChangeOrder(
            co_number=co_number,
            title=title,
            description=description,
            change_type=change_type,
            status=ChangeOrderStatus.DRAFT,
            created_date=date.today(),
            created_by=created_by,
            rfi_reference=rfi_reference,
            location=location
        )

        self.change_orders[co_number] = co
        return co

    def add_cost_item(self, co_number: str,
                     description: str,
                     quantity: float,
                     unit: str,
                     unit_cost: float,
                     category: str,
                     markup_percent: float = 0.0):
        """Add cost item to change order."""
        if co_number not in self.change_orders:
            raise ValueError(f"Change order {co_number} not found")

        co = self.change_orders[co_number]

        total = quantity * unit_cost * (1 + markup_percent)
        item = CostItem(
            description=description,
            quantity=quantity,
            unit=unit,
            unit_cost=unit_cost,
            total_cost=total,
            category=category,
            markup_percent=markup_percent
        )

        co.cost_items.append(item)
        self._recalculate_totals(co)

    def _recalculate_totals(self, co: ChangeOrder):
        """Recalculate change order totals."""
        co.direct_cost = sum(item.total_cost for item in co.cost_items)
        co.overhead_cost = co.direct_cost * self.overhead_rate
        co.profit_cost = (co.direct_cost + co.overhead_cost) * self.profit_rate
        co.total_cost = co.direct_cost + co.overhead_cost + co.profit_cost

    def set_schedule_impact(self, co_number: str, days: int,
                           affected_activities: List[str] = None):
        """Set schedule impact."""
        if co_number not in self.change_orders:
            raise ValueError(f"Change order {co_number} not found")

        co = self.change_orders[co_number]
        co.schedule_impact_days = days
        co.affected_activities = affected_activities or []

    def submit_for_review(self, co_number: str):
        """Submit change order for review."""
        if co_number not in self.change_orders:
            raise ValueError(f"Change order {co_number} not found")

        co = self.change_orders[co_number]
        if co.status != ChangeOrderStatus.DRAFT:
            raise ValueError("Can only submit draft change orders")

        co.status = ChangeOrderStatus.PENDING_REVIEW

    def submit_for_approval(self, co_number: str, reviewer: str, comments: str = ""):
        """Submit for approval after review."""
        if co_number not in self.change_orders:
            raise ValueError(f"Change order {co_number} not found")

        co = self.change_orders[co_number]
        if co.status != ChangeOrderStatus.PENDING_REVIEW:
            raise ValueError("Must be in review status")

        co.approvals.append(ApprovalRecord(
            approver_name=reviewer,
            approver_role="Reviewer",
            action="reviewed",
            action_date=datetime.now(),
            comments=comments
        ))

        co.status = ChangeOrderStatus.PENDING_APPROVAL

    def approve_change_order(self, co_number: str, approver: str,
                            approver_role: str, comments: str = ""):
        """Approve change order."""
        if co_number not in self.change_orders:
            raise ValueError(f"Change order {co_number} not found")

        co = self.change_orders[co_number]

        co.approvals.append(ApprovalRecord(
            approver_name=approver,
            approver_role=approver_role,
            action="approved",
            action_date=datetime.now(),
            comments=comments
        ))

        co.status = ChangeOrderStatus.APPROVED
        co.approved_date = date.today()
        co.approved_by = approver

    def reject_change_order(self, co_number: str, rejector: str,
                           reason: str):
        """Reject change order."""
        if co_number not in self.change_orders:
            raise ValueError(f"Change order {co_number} not found")

        co = self.change_orders[co_number]

        co.approvals.append(ApprovalRecord(
            approver_name=rejector,
            approver_role="Approver",
            action="rejected",
            action_date=datetime.now(),
            comments=reason
        ))

        co.status = ChangeOrderStatus.REJECTED

    def get_summary(self) -> Dict[str, Any]:
        """Generate change order summary."""
        cos = list(self.change_orders.values())

        by_status = {}
        by_type = {}
        total_approved = 0
        total_pending = 0
        total_schedule_impact = 0

        for co in cos:
            # By status
            status = co.status.value
            by_status[status] = by_status.get(status, 0) + 1

            # By type
            change_type = co.change_type.value
            by_type[change_type] = by_type.get(change_type, 0) + co.total_cost

            # Totals
            if co.status == ChangeOrderStatus.APPROVED:
                total_approved += co.total_cost
                total_schedule_impact += co.schedule_impact_days
            elif co.status in [ChangeOrderStatus.PENDING_REVIEW, ChangeOrderStatus.PENDING_APPROVAL]:
                total_pending += co.total_cost

        current_contract = self.original_contract + total_approved

        return {
            'project': self.project_name,
            'original_contract': self.original_contract,
            'approved_changes': total_approved,
            'current_contract': current_contract,
            'pending_changes': total_pending,
            'potential_contract': current_contract + total_pending,
            'total_change_orders': len(cos),
            'by_status': by_status,
            'by_type': by_type,
            'total_schedule_impact_days': total_schedule_impact,
            'change_percent': round(total_approved / self.original_contract * 100, 1) if self.original_contract > 0 else 0
        }

    def get_pending_approvals(self) -> List[ChangeOrder]:
        """Get change orders pending approval."""
        return [co for co in self.change_orders.values()
                if co.status in [ChangeOrderStatus.PENDING_REVIEW, ChangeOrderStatus.PENDING_APPROVAL]]

    def export_log(self, output_path: str):
        """Export change order log to Excel."""
        with pd.ExcelWriter(output_path, engine='openpyxl') as writer:
            # Summary
            summary = self.get_summary()
            summary_df = pd.DataFrame([
                {'Metric': 'Original Contract', 'Value': summary['original_contract']},
                {'Metric': 'Approved Changes', 'Value': summary['approved_changes']},
                {'Metric': 'Current Contract', 'Value': summary['current_contract']},
                {'Metric': 'Pending Changes', 'Value': summary['pending_changes']},
                {'Metric': 'Change %', 'Value': f"{summary['change_percent']}%"},
                {'Metric': 'Schedule Impact (days)', 'Value': summary['total_schedule_impact_days']}
            ])
            summary_df.to_excel(writer, sheet_name='Summary', index=False)

            # Change order list
            co_data = [co.to_dict() for co in self.change_orders.values()]
            pd.DataFrame(co_data).to_excel(writer, sheet_name='Change Orders', index=False)

            # Cost details
            cost_data = []
            for co in self.change_orders.values():
                for item in co.cost_items:
                    cost_data.append({
                        'CO Number': co.co_number,
                        'Description': item.description,
                        'Quantity': item.quantity,
                        'Unit': item.unit,
                        'Unit Cost': item.unit_cost,
                        'Total': item.total_cost,
                        'Category': item.category
                    })
            if cost_data:
                pd.DataFrame(cost_data).to_excel(writer, sheet_name='Cost Details', index=False)

        return output_path

Quick Start

# Initialize processor
processor = ChangeOrderProcessor(
    project_name="Office Tower",
    original_contract=50000000
)

# Create change order
co = processor.create_change_order(
    title="Additional Electrical Outlets",
    description="Add 50 electrical outlets per owner request",
    change_type=ChangeType.OWNER_REQUESTED,
    created_by="Project Manager"
)

# Add cost items
processor.add_cost_item(co.co_number, "Electrical outlets", 50, "EA", 150, "material")
processor.add_cost_item(co.co_number, "Installation labor", 25, "HR", 85, "labor")

# Set schedule impact
processor.set_schedule_impact(co.co_number, days=5)

# Submit for approval
processor.submit_for_review(co.co_number)

Common Use Cases

1. Process Approval

processor.submit_for_approval(co.co_number, "Reviewer", "Cost verified")
processor.approve_change_order(co.co_number, "Owner Rep", "Owner", "Approved per request")

2. Get Summary

summary = processor.get_summary()
print(f"Contract value: ${summary['current_contract']:,.0f}")
print(f"Change %: {summary['change_percent']}%")

3. Export Log

processor.export_log("change_order_log.xlsx")

Resources

• DDC Book: Chapter 3.1 - Cost Management
• Reference: AIA Document G701