RxPY - Operators

Working with Operators

You can work with multiple operators together using pipe() method. This method allows chaining multiple operators together.

Here, is a working example of using operators −

test = of(1,2,3) // an observable
subscriber = test.pipe(
   op1(),
   op2(),
   op3()
)

In the above example, we have created an observable using of() method that takes in values 1, 2 and 3. Now, on this observable, you can perform a different operation, using any numbers of operators using pipe() method as shown above. The execution of operators will go on sequentially on the observable given.

To work with operators, first import it as shown below −

from rx import of, operators as op

Here, is a working example −

testrx.py

from rx import of, operators as op
test = of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
sub1 = test.pipe(
   op.filter(lambda s: s%2==0),
   op.reduce(lambda acc, x: acc + x)
)
sub1.subscribe(lambda x: print("Sum of Even numbers is {0}".format(x)))

In the above example, there is a list of numbers, from which we are filtering even numbers using a filter operator and later adding it using a reduce operator.

Output

E:\pyrx>python testrx.py
Sum of Even numbers is 30

Here is a list of Operators, that we are going to discuss −

Creating Observables
Mathematical operators
Transformation operators
Filtering operators
Error handling operators
Utility operators
Conditional
Connectable
Combining operators

Creating Observables

Following are the observables, we are going to discuss in Creation category

Show Examples

Observable	Description
create	This method is used to create an observable.
empty	This observable will not output anything and directly emit the complete state.
never	This method creates an observable that will never reach the complete state.
throw	This method will create an observable that will throw an error.
from_	This method will convert the given array or object into an observable.
interval	This method will give a series of values produced after a timeout.
just	This method will convert given value into an observable.
range	This method will give a range of integers based on the input given.
repeat_value	This method will create an observable that will repeat the given value as per the count is given.
start	This method takes in a function as an input and returns an observable that will return value from the input function.
timer	This method will emit the values in sequence after the timeout is done.

Mathematical operators

The operators we are going to discuss in Mathematical operator category are as follows: −

Show Examples

Operator	Description
average	This operator will calculate the average from the source observable given and output an observable that will have the average value.
concat	This operator will take in two or more observables and given a single observable with all the values in the sequence.
count	This operator takes in an Observable with values and converts it into an Observable that will have a single value. The count function takes in predicate function as an optional argument. The function is of type boolean and will add value to the output only if it satisfies the condition.
max	This operator will give an observable with max value from the source observable.
min	This operator will give an observable with min value from the source observable.
reduce	This operator takes in a function called accumulator function that is used on the values coming from the source observable, and it returns the accumulated values in the form of an observable, with an optional seed value passed to the accumulator function.
sum	This operator will return an observable with the sum of all the values from source observables.

Transformation operators

The operators we are going to discuss in the Transformation operator category are mentioned below −

Show Examples

Operator	Category
buffer	This operator will collect all the values from the source observable, and emit them at regular intervals once the given boundary condition is satisfied.
ground_by	This operator will group the values coming from the source observable based on the key_mapper function given.
map	This operator will change each value from the source observable into a new value based on the output of the mapper_func given.
scan	This operator will apply an accumulator function to the values coming from the source observable and return an observable with new values.

Filtering operators

The operators we are going to discuss in Filtering operator category are given below −

Show Examples

Operator	Category
debounce	This operator will give the values from the source observable, until the timespan given and ignore the rest of the time passes.
distinct	This operator will give all the values that are distinct from the source observable.
element_at	This operator will give an element from the source observable for the index given.
filter	This operator will filter values from the source observable based on the predicate function given.
first	This operator will give the first element from the source observable.
ignore_elements	This operator will ignore all the values from the source observable and only execute calls to complete or error callback functions.
last	This operator will give the last element from the source observable.
skip	This operator will give back an observable that will skip the first occurrence of count items taken as input.
skip_last	This operator will give back an observable that will skip the last occurrence of count items taken as input.
take	This operator will give a list of source values in continuous order based on the count given.
take_last	This operator will give a list of source values in continuous order from last based on the count given.

Error handling operators

The operators we are going to discuss in the Error handling operator category are: -

Show Examples

Operator	Description
catch	This operator will terminate the source observable when there is an exception.
retry	This operator will retry on the source observable when there is an error and once the retry count is done it will terminate.

Utility operators

The following are the operators we are going to discuss in the Utility operator category.

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Operator	Description
delay	This operator will delay the source observable emission as per the time or date is given.
materialize	This operator will convert the values from the source observable with the values emitted in the form of explicit notification values.
time_interval	This operator will give the time elapsed between the values from the source observable.
timeout	This operator will give all the values from the source observable after the elapsed time or else will trigger an error.
timestamp	This operator will attach a timestamp to all the values from the source observable.

Conditional and Boolean operators

The operators we are going to discuss in Conditional and Boolean Operator category are as given below −

Show Examples

Operator	Description
all	This operator will check if all the values from the source observable satisfy the condition given.
contains	This operator will return an observable with the value true or false if the given value is present and if it is the value of the source observable.
default_if_empty	This operator will return a default value if the source observable is empty.
sequence_equal	This operator will compare two sequences of observables or an array of values and return an observable with the value true or false.
skip_until	This operator will discard values from the source observable until the second observable emits a value.
skip_while	This operator will return an observable with values from the source observable that satisfies the condition passed.
take_until	This operator will discard values from the source observable after the second observable emits a value or is terminated.
take_while	This operator will discard values from the source observable when the condition fails.

Connectable Operators

The operators we are going to discuss in Connectable Operator category are −

Show Examples

Operator	Description
publish	This method will convert the observable into a connectable observable.
ref_count	This operator will make the observable a normal observable.
replay	This method works similar to the replaySubject. This method will return the same values, even if the observable has already emitted and some of the subscribers are late in subscribing.

Combining Operators

The following are the operators we are going to discuss in the Combining operator category.

Show Examples

Operator	Description
combine_latest	This operator will create a tuple for the observable given as input.
merge	This operator will merge given observables.
start_with	This operator will take in the given values and add at the start of the source observable return back the full sequence.
zip	This operator returns an observable with values in a tuple form which is formed by taking the first value of the given observable and so on.

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