Research Environment
Object Store
Introduction
The Object Store is a file system that you can use in your algorithms to save, read, and delete data. The Object Store is organization-specific, so you can save or read data from the same Object Store in all of your organization's projects. The Object Store works like a key-value storage system where you can store regular strings, JSON encoded strings, XML encoded strings, and bytes. You can access the data you store in the Object Store from backtests, the Research Environment, and live algorithms.
Get All Stored Data
To get all of the keys and values in the Object Store, iterate through the object_store
property.
for kvp in qb.object_store: key = kvp.key value = kvp.value
To iterate through just the keys in the Object Store, iterate through the keys
property.
for key in qb.object_store.keys: continue
Save Data
The Object Store saves objects under a key-value system. If you save objects in backtests, you can access them from the Research Environment.
If you run algorithms in QuantConnect Cloud, you need storage create permissions to save data in the Object Store.
If you don't have data to store, create some sample data.
You can save Bytes
and string
objects in the Object Store.
Strings
To save a string
object, call the save
or save_string
method.
save_successful = qb.object_store.save(f"{qb.project_id}/string_key", string_sample)
JSON
XML
Bytes
To save a Bytes
object (for example, zipped data), call the save_bytes
method.
save_successful = qb.object_store.save_bytes(f"{qb.project_id}/bytes_key", bytes_sample) zipped_data_sample = Compression.zip_bytes(bytes(string_sample, "utf-8"), "data") zip_save_successful = qb.object_store.save_bytes(f"{qb.project_id}/bytesKey.zip", zipped_data_sample)
Read Data
To read data from the Object Store, you need to provide the key you used to store the object.
You can load Bytes
and string
objects from the Object Store.
Before you read data from the Object Store, check if the key exists.
if qb.object_store.contains_key(key): # Read data
Strings
To read a string
object, call the read
or read_string
method.
string_data = qb.object_store.read(f"{qb.project_id}/string_key")
JSON
XML
Bytes
To read a Bytes
object, call the read_bytes
method.
byte_data = qb.object_store.read_bytes(f"{qb.project_id}/bytes_key")
Delete Data
Delete objects in the Object Store to remove objects that you no longer need. If you use the Research Environment in QuantConnect Cloud, you need storage delete permissions to delete data from the Object Store.
To delete objects from the Object Store, call the delete
method. Before you delete data, check if the key exists. If you try to delete an object with a key that doesn't exist in the Object Store, the method raises an exception.
if qb.object_store.contains_key(key): qb.object_store.delete(key)
To delete all of the content in the Object Store, iterate through all the stored data.
for kvp in qb.object_store: qb.object_store.delete(kvp.key)
Cache Data
When you write to or read from the Object Store, the notebook caches the data. The cache speeds up the notebook execution because if you try to read the Object Store data again with the same key, it returns the cached data instead of downloading the data again. The cache speeds up execution, but it can cause problems if you are trying to share data between two nodes under the same Object Store key. For example, consider the following scenario:
- You open project A and save data under the key
123
. - You open project B and save new data under the same key
123
. - In project A, you read the Object Store data under the key
123
, expecting the data from project B, but you get the original data you saved in step #1 instead.
You get the data from step 1 instead of step 2 because the cache contains the data from step 1.
To clear the cache, call the Clear
method.
qb.object_store.clear()
Storage Quotas
If you use the Research Environment locally, you can store as much data as your hardware will allow. If you use the Research Environment in QuantConnect Cloud, you must stay within your storage quota. If you need more storage space, edit your storage plan.
Example for DataFrames
Follow these steps to create a DataFrame, save it into the Object Store, and load it from the Object Store:
- Get some historical data.
- Get the file path for a specific key in the Object Store.
- Call the to_csv method to save the DataFrame in the Object Store as a CSV file.
- Call the read_csv method to load the CSV file from the Object Store.
spy = qb.add_equity("SPY").symbol df = qb.history(qb.securities.keys, 360, Resolution.DAILY)
file_path = qb.object_store.get_file_path("df_to_csv")
df.to_csv(file_path) # File size: 32721 bytes
reread = pd.read_csv(file_path)
pandas
supports saving and loading DataFrame objects in the following additional formats:
- XML
- JSON
- Parquet
- Pickle
file_path = qb.object_store.get_file_path("df_to_xml") df.to_xml(file_path) # File size: 87816 bytes reread = pd.read_xml(file_path)
file_path = qb.object_store.get_file_path("df_to_json") df.to_json(file_path) # File size: 125250 bytes reread = pd.read_json(file_path)
file_path = qb.object_store.get_file_path("df_to_parquet") df.to_parquet(file_path) # File size: 23996 bytes reread = pd.read_parquet(file_path)
file_path = qb.object_store.get_file_path("df_to_pickle") df.to_pickle(file_path) # File size: 19868 bytes reread = pd.read_pickle(file_path)
Example for Plotting
You can use the Object Store to plot data from your backtests and live algorithm in the Research Environment. The following example demonstrates how to plot a Simple Moving Average indicator that's generated during a backtest.
- Create a algorithm, add a data subscription, and add a simple moving average indicator.
- Save the indicator data as
string
inself.content
. - In the OnEndOfAlgorithm method, save the indicator data to the Object Store.
- Open the Research Environment and create a
QuantBook
. - Read the indicator data from the Object Store.
- Convert the data to a pandas object and create a chart.
class ObjectStoreChartingAlgorithm(QCAlgorithm): def initialize(self): self.add_equity("SPY") self.content = '' self._sma = self.sma("SPY", 22)
The algorithm will save self.content
to the Object Store.
def on_data(self, data: Slice): self.plot('SMA', 'Value', self.sma.current.value) self.content += f'{self.sma.current.end_time},{self.sma.current.value}\n'
def on_end_of_algorithm(self): self.object_store.save('sma_values_python', self.content)
qb = QuantBook()
content = qb.object_store.read("sma_values_python")
The key you provide must be the same key you used to save the object.
data = {} for line in content.split('\n'): csv = line.split(',') if len(csv) > 1: data[csv[0]] = float(csv[1]) series = pd.Series(data, index=data.keys()) series.plot()
class ObjectStoreChartingAlgorithm(QCAlgorithm): def initialize(self) -> None: self.set_start_date(2023, 1, 1) # Set Start Date self.set_cash(100000) # Set Strategy Cash self.add_equity("SPY", Resolution.MINUTE) self.content = '' # Create SMA indicator for referencing. self.sma = self.SMA("SPY", 22) def on_data(self, data: Slice) -> None: # Cache the indicator data point to save it. self.content += f'{self.sma.current.end_time},{self.sma.current.value}\n' def on_end_of_algorithm(self) -> None: # Save the indicator values to object store for logging. self.object_store.save('sma_values_python', self.content)