dilemma 0.3.4

This is an expression language python package.

Dilemma Expression Language

A secure, powerful expression evaluation engine for Python applications that makes complex logical expressions readable and maintainable.

Why Dilemma?

Instead of writing complex Python conditionals like this:

if (user.get('profile', {}).get('age', 0) >= 18 and 
    user.get('subscription', {}).get('status') == 'active' and
    datetime.now() - user.get('last_login', datetime.min) < timedelta(days=30)):
    # grant access
    pass

Write this:

from dilemma import evaluate

expr = "user.profile.age >= 18 and user.subscription.status == 'active' and user.last_login upcoming within 30 days"

if evaluate(expr, context):
    # grant access
    pass

Features

• Secure evaluation - No arbitrary code execution, only safe expressions
• Rich data access - Navigate nested dictionaries and lists with ease
• Date/time operations - Natural language date comparisons
• Multiple resolvers - JsonPath, JQ, and basic dictionary lookup
• Performance optimized - Compile expressions once, evaluate many times
• Type safe - Built-in type checking and validation

Quick Start

pip install dilemma

from dilemma import evaluate

# Basic arithmetic and logic
result = evaluate("2 * (3 + 4)")  # Returns 14
result = evaluate("age >= 18 and status == 'active'", {"age": 25, "status": "active"})

# Date operations
result = evaluate("user.last_login upcoming within 7 days", context)
result = evaluate("subscription.end_date is $future", context)

# Complex data access
result = evaluate("user.permissions contains 'admin'", context)
result = evaluate("`[.users[] | select(.active == true) | .name] | length` > 0", context)

Language Features

All Language Features. Extensive Examples.

Data Access Patterns

# Dot notation for nested objects
"user.profile.settings.theme == 'dark'"

# Natural possessive syntax  
"user's subscription's status == 'premium'"

# Array/list access
"users[0].name == 'Alice'"

# Check membership
"'admin' in user.roles"
"user.permissions contains 'read'"

Date and Time Operations

# Relative time checks
"user.created_at upcoming within 30 days"
"order.shipped_date older than 1 week"

# State comparisons
"subscription.expires is $future"
"last_backup is $past"
"meeting.date is $today"

# Date comparisons
"start_date before end_date"
"event.date same_day_as $now"

Advanced JQ Integration

For complex data manipulation, use JQ expressions in backticks:

# Filter and transform arrays - working with provided context
evaluate('`[.users[] | select(.active == true) | .name]`', context)

# Mathematical operations on arrays  
evaluate('`[.sales[].amount] | add` > 10000', context)

# Complex conditionals
evaluate('`[.products[] | select(.price > 100 and .category == "electronics")] | length` > 1', context)

Performance Optimization

For repeated evaluations, compile expressions once:

from dilemma import compile_expression

# Compile once
eligibility_check = compile_expression(
    "user.age >= 18 and user.subscription.active and user.last_login upcoming within 30 days"
)

# Evaluate many times with different contexts
for user_data in users:
    if eligibility_check.evaluate(user_data):
        # send_premium_content(user_data)
        pass

Error Handling

Dilemma provides clear, actionable error messages:

try:
    result = evaluate("user.invalidfield == 'test'", context)
except VariableError as e:
    print(f"Expression error: {e}")
    # Suggests available fields and common fixes

Use Cases

• Form validation rules - "email like '*@*' and age >= 13"
• Business logic - "order.total > 100 and customer.tier == 'premium'"
• Access control - "user.roles contains 'admin' or resource.owner == user.id"
• Data filtering - "created_at upcoming within 24 hours and status == 'pending'"
• Workflow conditions - "approval.status == 'approved' and budget.remaining >= cost"

Safety & Security

• ✅ No arbitrary Python code execution
• ✅ No access to imports or builtins
• ✅ Sandboxed evaluation environment
• ✅ Input validation and sanitization
• ✅ Memory and complexity limits

License

MIT License - see LICENSE file for details.