Guide

Give’s syntax

There are multiple ways you can use give(). give returns None unless it is given a single positional argument, in which case it returns the value of that argument.

  • give(key=value)

    This is the most straightforward way to use give: you write out both the key and the value associated.

    Returns: None

  • x = give(value)

    When no key is given, but the result of give is assigned to a variable, the key is the name of that variable. In other words, the above is equivalent to give(x=value).

    Returns: The value

  • give(x)

    When no key is given and the result is not assigned to a variable, give(x) is equivalent to give(x=x). If the argument is an expression like x * x, the key will be the string "x * x".

    Returns: The value

  • give(x, y, z)

    Multiple arguments can be given. The above is equivalent to give(x=x, y=y, z=z).

    Returns: None

  • x = value; give()

    If give has no arguments at all, it will look at the immediately previous statement and infer what you mean. The above is equivalent to x = value; give(x=value).

    Returns: None

Time and code location

  • give.line(...) emits, in addition to the rest, {"$line": location_info} where location_info is a LinePosition object that corresponds to where give.line was called.

  • give.time(...) emits, in addition to the rest, {"$time": time.time()}

Wrapping

Use the wrap() method to create blocks in which other context managers can be plugged:

@contextmanager
def hello():
    print("hello!")
    yield
    print("bye!")

with given() as gv:

    gv.wrap("main", hello)

    with give.wrap("main"):
        print(":)")

# prints:
# hello!
# :)
# bye!

Customization

Custom versions of give can be created with giver(). For example, givex = giver("x", y=7); givex(2) would emit {"x": 2, "y": 7}. You can also create give/given pairs with make_give().

Important methods

The important methods listed here are those you should know in order to be immediately productive with Giving. They are available on the given() object. Unless otherwise specified, assume we are inside a block defined by with given() as gv: ....

  • print() and display(): Print the stuff to the terminal. display looks nicer, but print has more flexible formatting.

    gv.print("x = {x}, y = {y:.2%}")

  • accum(): This returns a list to which the stream’s dicts will be appended. This allows you to do anything you want that can be done with a list, like reductions or plotting. Giving provides a battery of operators that might do the job better, but if you have trouble with the paradigm or can’t be bothered, this is an easy escape hatch.

    results = gv.accum()
...
print(sum(data["x"] for data in results if "x" in data))

  • values(): Context manager which accumulates all values into a list (with given().values() as vals: ... is essentially the same as with given() as gv: vals = gv.accum() ...).

    with given()["?x"].values() as results:
    ...

print(sum(results))

  • subscribe() and ksubscribe(): Do stuff with the data as it comes. The difference between subscribe and ksubscribe is that the former is called with one argument, which is the next entry in the stream, whereas the latter assumes that all the elements are dicts, and the function is called with **kwargs syntax.

    Note

    ksubscribe will wrap the function with lax_function() so that it has an implicit **kwargs argument at the end, to make your life easier. That way, any keys that are not useful to your function are simply ignored.

    # Compare
@gv.subscribe
def pr(data):
    print("x = {x}, y = {y}".format(data))

# to:
@gv.ksubscribe
def pr(x, y):
    print(f"x = {x}, y = {y}")

  • gv[key], gv["?key"]: Extracts all the values for a key.

    • Without a leading ?, e.g. gv["x"], every entry must have the key.

    • With a leading ?, e.g. gv["?x"], entries that don’t have the key are ignored. This is often the more useful syntax.

    gv["?x"].print()

  • where(), where_any(), keep(): These operators filter entries depending on the keys they have and their values.

    • where returns entries where all keys are present, and conditions are met

    • where_any returns entries where any key is present (does not support conditions)

    • keep returns entries where any key is present and drops all other keys; no conditions, but it can remap key names

    gv.where("x", "y", z=True).print()

Selected operators

Here is a classification of available operators.

Filtering

  • filter(): filter with a function

  • kfilter(): filter with a function (keyword arguments)

  • where(): filter based on keys and simple conditions

  • where_any(): filter based on keys

  • keep(): filter based on keys (+drop the rest)

  • distinct(): only emit distinct elements

  • norepeat(): only emit distinct consecutive elements

  • first(): only emit the first element

  • last(): only emit the last element

  • take(): only emit the first n elements

  • take_last(): only emit the last n elements

  • skip(): suppress the first n elements

  • skip_last(): suppress the last n elements

Mapping

  • map(): map with a function

  • kmap(): map with a function (keyword arguments)

  • augment(): add extra keys using a mapping function

  • getitem(): extract value for a specific key

  • sole(): extract value from dict of length 1

  • as_(): wrap as a dict

Reduction

  • reduce(): reduce with a function

  • scan(): emit a result at each reduction step

  • roll(): reduce using overlapping windows

  • kmerge(): merge all dictionaries in the stream

  • kscan(): incremental version of kmerge

Arithmetic reductions

Most of these reductions can be called with the scan argument set to True to use scan instead of reduce. scan can also be set to an integer, in which case roll is used.

Wrapping

Timing

  • debounce(): suppress events that are too close in time

  • sample(): sample an element every n seconds

  • throttle(): emit at most once every n seconds

Debugging

  • breakpoint(): set a breakpoint whenever data comes in. Use this with filters.

  • tag(): assigns a special word to every entry. Use with breakword.

  • breakword(): set a breakpoint on a specific word set by tag, using the BREAKWORD environment variable.

  • print(): print out the stream.

  • display(): print out the stream (pretty).

  • accum(): accumulate into a list.

  • values(): accumulate into a list (context manager).

  • subscribe(): run a task on every element.

  • ksubscribe(): run a task on every element (keyword arguments).