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+# Subscribing to order book changes
+
+The Python API includes three functions for working with the [order book](/en/book/automation/marketbook).
+
+bool market_book_add(symbol)
+
+The market_book_add function subscribes to receive events about order book changes for the specified symbol. The name of the required financial instrument is indicated in a single unnamed parameter.
+
+The function returns a boolean success indication.
+
+The function is an analog of [MarketBookAdd](/en/book/automation/marketbook/marketbook_add_release). After completing work with the order book, the subscription should be canceled by calling market_book_release (see further).
+
+tuple[] market_book_get(symbol)
+
+The market_book_get function requests the current contents of the order book for the specified symbol. The result is returned as a tuple (array) of BookInfo records. Each entry is an analog of the MqlBookInfo structure, and from the Python point of view, this is a named tuple with the fields "type", "price", "volume", "volume_real". In case of an error, the None value is returned.
+
+Note that for some reason in Python, the field is called volume_dbl, although in MQL5 the corresponding field is called volume_real.
+
+To work with this function, you must first subscribe to receive order book events using the market_book_add function.
+
+The function is an analog of [MarketBookGet](/en/book/automation/marketbook/marketbook_get). Please note that a Python script cannot receive OnBookEvent events directly and should poll the contents of the glass in a loop.
+
+bool market_book_release(symbol)
+
+The market_book_release function cancels the subscription for order book change events for the specified symbol. On success, the function returns True. The function is an analog of [MarketBookRelease](/en/book/automation/marketbook/marketbook_add_release).
+
+Let's take a simple example (see MQL5/Scripts/MQL5Book/Python/eurusdbook.py).
+
+```
+import MetaTrader5 as mt5
+import time               # connect a pack for the pause
+   
+# let's establish a connection to the MetaTrader 5 terminal
+if not mt5.initialize():
+   print("initialize() failed, error code =", mt5.last_error())
+   mt5.shutdown()
+   quit()
+   
+# subscribe to receive DOM updates for the EURUSD symbol
+if mt5.market_book_add('EURUSD'):
+   # run 10 times a loop to read data from the order book
+   for i in range(10):
+      # get the contents of the order book
+      items = mt5.market_book_get('EURUSD')
+      # display the entire order book in one line as is
+      print(items)
+      # now display each price level separately in the form of a dictionary, for clarity
+      for it in items or []:
+         print(it._asdict())
+      # let's pause for 5 seconds before the next request for data from the order book
+      time.sleep(5) 
+   # unsubscribe to order book changes
+   mt5.market_book_release('EURUSD')
+else:
+   print("mt5.market_book_add('EURUSD') failed, error code =", mt5.last_error())
+   
+# complete the connection to the MetaTrader 5 terminal
+mt5.shutdown()
+
+```
+
+An example of the result:
+
+```
+(BookInfo(type=1, price=1.20036, volume=250, volume_dbl=250.0), BookInfo(type=1, price=1.20029, volume=100, volume...
+{'type': 1, 'price': 1.20036, 'volume': 250, 'volume_dbl': 250.0}
+{'type': 1, 'price': 1.20029, 'volume': 100, 'volume_dbl': 100.0}
+{'type': 1, 'price': 1.20028, 'volume': 50, 'volume_dbl': 50.0}
+{'type': 1, 'price': 1.20026, 'volume': 36, 'volume_dbl': 36.0}
+{'type': 2, 'price': 1.20023, 'volume': 36, 'volume_dbl': 36.0}
+{'type': 2, 'price': 1.20022, 'volume': 50, 'volume_dbl': 50.0}
+{'type': 2, 'price': 1.20021, 'volume': 100, 'volume_dbl': 100.0}
+{'type': 2, 'price': 1.20014, 'volume': 250, 'volume_dbl': 250.0}
+(BookInfo(type=1, price=1.20035, volume=250, volume_dbl=250.0), BookInfo(type=1, price=1.20029, volume=100, volume...
+{'type': 1, 'price': 1.20035, 'volume': 250, 'volume_dbl': 250.0}
+{'type': 1, 'price': 1.20029, 'volume': 100, 'volume_dbl': 100.0}
+{'type': 1, 'price': 1.20027, 'volume': 50, 'volume_dbl': 50.0}
+{'type': 1, 'price': 1.20025, 'volume': 36, 'volume_dbl': 36.0}
+{'type': 2, 'price': 1.20023, 'volume': 36, 'volume_dbl': 36.0}
+{'type': 2, 'price': 1.20022, 'volume': 50, 'volume_dbl': 50.0}
+{'type': 2, 'price': 1.20021, 'volume': 100, 'volume_dbl': 100.0}
+{'type': 2, 'price': 1.20014, 'volume': 250, 'volume_dbl': 250.0}
+(BookInfo(type=1, price=1.20037, volume=250, volume_dbl=250.0), BookInfo(type=1, price=1.20031, volume=100, volume...
+{'type': 1, 'price': 1.20037, 'volume': 250, 'volume_dbl': 250.0}
+{'type': 1, 'price': 1.20031, 'volume': 100, 'volume_dbl': 100.0}
+{'type': 1, 'price': 1.2003, 'volume': 50, 'volume_dbl': 50.0}
+{'type': 1, 'price': 1.20028, 'volume': 36, 'volume_dbl': 36.0}
+{'type': 2, 'price': 1.20025, 'volume': 36, 'volume_dbl': 36.0}
+{'type': 2, 'price': 1.20023, 'volume': 50, 'volume_dbl': 50.0}
+{'type': 2, 'price': 1.20022, 'volume': 100, 'volume_dbl': 100.0}
+{'type': 2, 'price': 1.20016, 'volume': 250, 'volume_dbl': 250.0}
+...
+
+```