Asynchronous Methods

A Firebase instance has different methods that let you transact with it. The methods shown below are Asynchronous. This means that:

• Python won’t wait for the response, it will continue executing following lines of code
• You should NOT assign return value to a variable. Doing this will always assign None
• You will have to use a callback to manipulate returned data from a request

Note: There are also Synchronous methods you can use. Read along to see how to use them.

.get(**kwargs)

Get data a particular location on your Firebase

• Requires:
  • point=”location_to_read”
  • auth=”access_token” (Optional)
  • callback=name_of_a_function (Optional)
  • callbacks=[list_of_callbacks] (Optional)
  • error=name_of_a_function (Optional)
• Returns None. Data fetched is passed to the callback function, if specified.

Example:

# Callback function definition
def hello(data):
    print(data)

# Another Callback
def world(data):
    with open('/home/user/.firebase-data', 'w') as data_file:
        data_file.write(data)

# Making a 'GET' request
my_firebase.get(point="/child", auth="Ja2f29f4Gsk2d3bhxW2d8vDlK", callback=hello)

# A Request with multiple callbacks
my_firebase,get(point="/child", auth="Ja2f29f4Gsk2d3bhxW2d8vDlK", callbacks=[hello, world])

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.put(**kwargs)

Write data into your Firebase

• Requires:
  • point=”location_to_read”
  • data=”data_to_put”
  • auth=”access_token” (Optional)
  • callback=name_of_a_function (Optional)
  • callbacks=[list_of_callbacks] (Optional)
  • error=name_of_a_function (Optional)
• Returns None. Data you just put is passed to the callback function, if specified.

---

.delete(**kwargs)

Delete data from your Firebase

• Requires:
  • point=”location_to_delete”
  • auth=”access_token” (Optional)
  • callback=name_of_a_function (Optional)
  • callbacks=[list_of_callbacks] (Optional)
  • error=name_of_a_function (Optional)
• Returns None. A string saying null is passed to the callback function, if specified.

---

.export(**kwargs)

Export data from a location on your Firebase

• Requires:
  • point=”location_to_read”
  • auth=”access_token” (Optional)
  • path=”UNIX_path_to_file_to_write_to” (Optional)
  • callback=name_of_a_function (Optional)
  • callbacks=[list_of_callbacks] (Optional)
  • error=name_of_a_function (Optional)
• Returns None. Data you just exported is passed to the callback function, if specified.

Note: if the path argument is not given, this will behave similar to get() method of the Firebase instance.

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.onChange(**kwargs)

Poll for changes at a Location on your Firebase.

• Requires:
  • point=”location_to_read”
  • auth=”access_token” (Optional)
  • callback=name_of_a_function (Optional)
  • callbacks=[list_of_callbacks] (Optional)
  • error=name_of_a_function (Optional)
  • ignore_error=True (Optional) - Whether to keep watching incase of an error or make it Stop
  • frequency=10 (Optional) - The number of seconds between checks on the Firebase
  • fetches=-1 (Optional) - The number of times to look at the Firebase before automatically stopping. It is a positive integer. Giving a negative integer makes it be ignored.
• Returns an Object representing the Watch. This object has one method:
  • .stop(number_of_seconds) - Passing an integer will cause the watch to be stopped after the specified number of seconds. If no number is passed, the watch will be stopped as soon as Possible.

def keep_printing(data):
    print(data)

# Creates a watch Object
watch = my_firebase.onChange(point="/watch_here", callback=keep_printing) 
watch.stop(20) # The Watch will be stopped after 20 seconds

Note:

• there’s No synchronous flavor of this method. For obvious reasons.
• the stopping of a watch may take longer or shorter time for the action to kick in. This depends on your System.

Callbacks and Errors

In all the asynchronous methods, a Callback can be assigned. The callback will be executed once response is received. In the case of .onChange() method, the callback will be called every time data changes at the point specified.

Since version 0.1.2, multiple callbacks may be assigned using the callbacks parameter. The methods/functions, placed in a list and passed to the Firebase methods, will be executed sequentially as ordered in the particular list.

Functions assigned to error are executed when an error occurs while executing the action. The following errors may be caught:

1. EnvironmentError: This is caused by Trying to access a non-existant Firebase or Security Rules violation while trying to execute a query
2. KeyError: This is caused when you do not pass a required argument to any function
3. ConnectionError: This will occur mostly due to Network problems

If you wanted to catch errors according to this classes, you could do:

def caught_an_error(err):
    if err.__class__.__name__ == "KeyError":
        print("KeyError: " + str(err))
    elif err.__class__.__name__ == "EnvironmentError":
        print("EnvironmentError: " + str(err))
    elif err.__class__.__name__ == "ConnectionError":
        print("ConnectionError: " + str(err))
    else:
        print(err.__class__.__name__ + str(err))

Note: All callbacks and error handling functions should be defined before assigning them to a method.