Automated Trading Development in Python, Backtesting with Pandas and Zipline

The development of automated trading systems is an attractive topic for many traders and investors. With advancements in technical analysis and data analysis, many people are saving time and effort through automated strategies. In this article, we will explore in detail the development of an automated trading system using Python and the backtesting method using
Pandas and Zipline.

1. Concept of Automated Trading

Automated trading refers to a system that automatically makes investment decisions according to a set of rules. It can be applied to various assets such as stocks, foreign exchange, and cryptocurrencies, allowing traders to quickly gather and analyze market data through algorithms and programs to make trading decisions. This reduces emotional decisions and human errors, enabling data-driven decisions.

2. Introduction to Pandas and Zipline

2.1 Pandas

Pandas is a Python library for data analysis, which provides an easy way to process various forms of data through a data structure called DataFrame. It is very useful for tasks related to financial data, such as stock data processing and time series data analysis.

2.2 Zipline

Zipline is an open-source backtesting library written in Python. Developed as a core component of Quantopian, it provides functionalities for users to simulate and test proposed strategies. Zipline allows clear definitions of trading logic and emulates execution costs, slippage, and trading volume, offering more realistic test results.

3. Setting Up the Development Environment

To develop an automated trading system, you need to set up a development environment.
Below is a method for installing the required libraries and setting up the basic environment.

pip install pandas zipline

4. Preparing the Data

For backtesting, historical asset price data must be prepared.
You can obtain data through Yahoo Finance or the Alpha Vantage API.
Here, we will show how to use a CSV file obtained from Yahoo Finance and convert it into a DataFrame.

import pandas as pd

# Read data from CSV file
data = pd.read_csv('data.csv')

# Convert date
data['Date'] = pd.to_datetime(data['Date'])
data.set_index('Date', inplace=True)

# Display data
print(data.head())

5. Backtesting Using Zipline

I will explain how to implement a basic trading strategy for backtesting using Zipline.
I will illustrate with the simplest trading strategy: the moving average crossover.

5.1 Defining the Trading Strategy

The moving average crossover strategy involves buying when the short-term moving average crosses above the long-term moving average and selling when it crosses below. The following is the Zipline code that implements this strategy.

from zipline.api import order, record, symbol
from zipline import run_algorithm
import pandas as pd
import numpy as np

def initialize(context):
    context.asset = symbol('AAPL')

def handle_data(context, data):
    # Calculate 50-day and 200-day moving averages
    short_mavg = data.history(context.asset, 'price', 50, '1d').mean()
    long_mavg = data.history(context.asset, 'price', 200, '1d').mean()
    
    # Buying and selling logic
    if short_mavg > long_mavg and not context.portfolio.positions[context.asset]:
        order(context.asset, 10)  # Buy 10 shares
    elif short_mavg < long_mavg and context.portfolio.positions[context.asset]:
        order(context.asset, -10)  # Sell 10 shares

def analyze(context, perf):
    import matplotlib.pyplot as plt
    perf[['portfolio_value']].plot()
    plt.title('Portfolio Value Over Time')
    plt.show()

# Get data (when using csv files)
data = pd.read_csv('data.csv', parse_dates=True, index_col='Date')
data = data[['Close']].rename(columns={'Close': 'price'})

start = pd.Timestamp('2020-01-01')
end = pd.Timestamp('2021-01-01')

# Run Zipline
run_algorithm(start=start, end=end, initialize=initialize, 
               handle_data=handle_data, 
               data_frequency='daily', 
               capital_base=10000, 
               bundle='quantopian-quandl')  # Set data bundle

6. Analyzing Results

After completing the backtest, performance analysis is necessary. Zipline provides metrics such as returns, maximum drawdown, and Sharpe ratio.
By evaluating the strategy's effectiveness through these metrics, adjustments can be made to the strategy, followed by re-testing if necessary.

7. Conclusion

In this article, we have described how to implement a basic automated trading strategy using Python and Zipline and how to perform backtesting.
Developing an automated trading system is a process that requires iterative testing and improvement. Therefore, it is important to develop your own strategies and continually update them.
Automatized investing can greatly enhance your potential returns and mitigate human error, allowing you to make more calculated
investment decisions in the trading arena.

8. Additional Resources and References

- Zipline Official Documentation
- Pandas Official Documentation
- Quantopian Platform (currently out of service)
- Yahoo Finance