---
title: "Exponential Moving Average"
description: "This indicator represents the traditional exponential moving average indicator (EMA). When the indicator is ready, the first va..."
canonical: https://www.quantconnect.com/docs/v2/writing-algorithms/indicators/supported-indicators/exponential-moving-average
markdown: https://www.quantconnect.com/docs/v2/writing-algorithms/indicators/supported-indicators/exponential-moving-average.md
language: python
source: https://github.com/QuantConnect/Documentation/tree/master/03%20Writing%20Algorithms/28%20Indicators/01%20Supported%20Indicators/039%20Exponential%20Moving%20Average
modified: 2026-10-31
index: https://www.quantconnect.com/llms.txt
---

# Exponential Moving Average

[Documentation](https://www.quantconnect.com/docs/v2.md) > [Writing Algorithms](https://www.quantconnect.com/docs/v2/writing-algorithms.md) > Indicators > [Supported Indicators](https://www.quantconnect.com/docs/v2/writing-algorithms/indicators/supported-indicators.md) > Exponential Moving Average

> Code examples are shown in Python. Append `?lang=csharp` to this URL for the C# version of this page.

## Introduction

This indicator represents the traditional exponential moving average indicator (EMA). When the indicator is ready, the first value of the EMA is equivalent to the simple moving average. After the first EMA value, the EMA value is a function of the previous EMA value. Therefore, depending on the number of samples you feed into the indicator, it can provide different EMA values for a single security and lookback period. To make the indicator values consistent across time, warm up the indicator with all the trailing security price history.

To view the implementation of this indicator, see the [LEAN GitHub repository](https://github.com/QuantConnect/Lean/tree/master/Indicators/ExponentialMovingAverage.cs).

## Using EMA Indicator

To create an automatic indicator for `ExponentialMovingAverage`, call the `ema` helper method from the `QCAlgorithm` class. The `ema` method creates a `ExponentialMovingAverage` object, hooks it up for automatic updates, and returns it so you can used it in your algorithm. In most cases, you should call the helper method in the `initialize` method.

```python
class ExponentialMovingAverageAlgorithm(QCAlgorithm):
    def initialize(self) -> None:
        self._symbol = self.add_equity("SPY", Resolution.DAILY).symbol
        self._ema = self.ema(self._symbol, 20, 0.5)

    def on_data(self, slice: Slice) -> None:

        if self._ema.is_ready:
            # The current value of self._ema is represented by self._ema.current.value
            self.plot("ExponentialMovingAverage", "ema", self._ema.current.value)
```

For more information about this method, see the [QCAlgorithm class](https://www.lean.io/docs/v2/lean-engine/class-reference/py/QuantConnect/Algorithm/QCAlgorithm/#QuantConnect.Algorithm.QCAlgorithm.ema).

You can manually create a `ExponentialMovingAverage` indicator, so it doesn't automatically update. Manual indicators let you update their values with any data you choose.

Updating your indicator manually enables you to control when the indicator is updated and what data you use to update it. To manually update the indicator, call the `update` method. The indicator will only be ready after you prime it with enough data.

```python
class ExponentialMovingAverageAlgorithm(QCAlgorithm):
    def initialize(self) -> None:
        self._symbol = self.add_equity("SPY", Resolution.DAILY).symbol
        self._exponentialmovingaverage = ExponentialMovingAverage(20, 0.5)

    def on_data(self, slice: Slice) -> None:
        bar = slice.bars.get(self._symbol)
        if bar:
            self._exponentialmovingaverage.update(bar.end_time, bar.close)

        if self._exponentialmovingaverage.is_ready:
            # The current value of self._exponentialmovingaverage is represented by self._exponentialmovingaverage.current.value
            self.plot("ExponentialMovingAverage", "exponentialmovingaverage", self._exponentialmovingaverage.current.value)
```

For more information about this indicator, see its [reference](https://www.lean.io/docs/v2/lean-engine/class-reference/py/QuantConnect/Indicators/ExponentialMovingAverage).

## Visualization

The following plot shows values for some of the `ExponentialMovingAverage` indicator properties:

![ExponentialMovingAverage line plot.](https://cdn.quantconnect.com/docs/i/writing-algorithms/indicators/supported-indicators/exponential-moving-average.png)

## Indicator History

To get the historical data of the `ExponentialMovingAverage` indicator, call the `self.indicator_history` method. This method resets your indicator, makes a [history request](https://www.quantconnect.com/docs/v2/writing-algorithms/historical-data/history-requests.md), and updates the indicator with the historical data. Just like with regular history requests, the `indicator_history` method supports time periods based on a trailing number of bars, a trailing period of time, or a defined period of time. If you don't provide a `resolution` argument, it defaults to match the resolution of the security subscription.

```python
class ExponentialMovingAverageAlgorithm(QCAlgorithm):
    def initialize(self) -> None:
        self._symbol = self.add_equity("SPY", Resolution.DAILY).symbol
        self._ema = self.ema(self._symbol, 20, 0.5)

        indicator_history = self.indicator_history(self._ema, self._symbol, 100, Resolution.MINUTE)
        timedelta_indicator_history = self.indicator_history(self._ema, self._symbol, timedelta(days=10), Resolution.MINUTE)
        time_period_indicator_history = self.indicator_history(self._ema, self._symbol, datetime(2024, 7, 1), datetime(2024, 7, 5), Resolution.MINUTE)
```