Backtest Execution Model

EasyQuant uses an event-driven backtest model, consistent with JoinQuant / Zipline. Understanding the execution model helps avoid common pitfalls such as look-ahead bias and memory issues.

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Strategy Skeleton

Every strategy consists of three functions + one global object:

Component	When Called	Responsibility
initialize(context)	Once at backtest start	Set benchmark, commissions, register scheduled functions, initialize variables
handle_data(context, data)	Once per trading day	Read market data, evaluate signals, place orders
market_open(context)	Registered via run_daily	Custom entry point replacing handle_data
g	Persists across trading days	Store strategy variables (e.g., holding days, thresholds)

Daily Execution Flow

Each trading day:
  ┌─ before_trading_start(ctx, data)    ← Pre-market callback (optional)
  │
  ├─ run_daily / run_weekly / run_monthly  ← Scheduled functions
  │
  ├─ handle_data(context, data)           ← Daily trading logic
  │
  └─ after_trading_end(ctx, data)         ← Post-market callback (optional)

Key Constraints

Constraint	Description	Design Intent
T+1	Shares bought today can only be sold starting the next trading day	Complies with A-share trading rules; handled automatically by the framework
100-share multiples	Buy quantities are automatically rounded down to the nearest multiple of 100	Complies with A-share minimum lot size
Look-ahead bias prevention	Strategies can only access data up to and including context.current_dt	Ensures credible backtest results
Next-day execution	order* calls are enqueued during the current callback and filled at the next trading day's open	Avoids the bias of placing orders at the current day's close
Memory limit	Default 1024 MB limit, adjustable via max_memory_mb	Prevents OOM in large backtests

Order Execution Semantics

def market_open(context):
    # 1. Current moment: only places the order, does not fill immediately
    order_value('601390', 50000)

    # 2. Next trading day open: engine matches at the opening price
    #    - Checks available cash
    #    - Rounds to 100-share lots
    #    - Calculates commissions
    #    - Updates positions and cash

This means:

• You cannot read the fill price immediately after placing an order — the fill price is only available in the next callback
• Shares bought today cannot be sold today — closeable_amount is only greater than 0 on the T+1 day
• Strategy signals lead executions by one day — this is intentional, ensuring conservative and credible backtest results

The g Global Object

g is strategy-level persistent storage that survives across trading days. Suitable for storing:

• Strategy parameters (moving average periods, thresholds, etc.)
• State variables (holding days, last signal, etc.)
• Pre-computed stock universes

def initialize(context):
    g.security = '601390'
    g.hold_days = 0
    g.last_signal = None

def market_open(context):
    g.hold_days += 1  # Persists across days

Do not use Python global variables

Use g instead of Python global variables. g is managed by the framework, ensuring consistent behavior across backtests and paper trading.