Quickstart¶

Eager to get started? This page gives a good introduction to Injectify. Follow Installation to set up a project and install Injectify first.

A Minimal Application¶

Injecting code with Injectify is very simple.

from injectify import inject, HeadInjector

def foo(x):
    return x

print(foo(10))  # 10

@inject(target=foo, injector=HeadInjector())
def handler():
    x = 9000

print(foo(10))  # 9000

So what does this code do?

We begin by importing from the injectify module.
Next we defined a function foo that we will inject code into.
When we print the result of foo(10), we get 10.
We then use the inject() decorator. The first argument is the target object. This is the object that will have code injected into. The second argument is the injector. An injector is used to indicate the point at which the target object should be injected. Here we use the HeadInjector for our injector. This injector indicates that the code should be injected at the top of the target object.
Then we defined a function handler. The body of this function is the code that will be injected into foo.
Now when we print the result of foo(10), we get 9000.

Thus, after we inject the body of handler, the function foo then has the following code:

def foo(x):
    x = 9000
    return x

Injection Points¶

The first thing we need to be able to do is identify parts of the target object. Let’s decorate a function with markers which show some of the areas we are able to easily identify.

def bar():
    # HEAD

    def wrapper():  # NESTED
        pass

    x = 10  # FIELD

    if x > 10:
        # RETURN
        return True
    else:
        # RETURN
        return False

    # TAIL

The markers indicate parts of the object’s anatomy:

HEAD indicates the point at the top of the target object.
TAIL indicates the point at the bottom of the target object.
FIELD indicates the point at a field’s assignment.
RETURN indicates the point before a return statement.
NESTED indicates a nested function.

Note

Not all Python objects have all these injection points. For example, a module does not have a return statement, so a module has no RETURN marker.

Injectors¶

The injector you use tells Injectify the injection point to use when merging the code inside the target object. Each of the markers above has a corresponding injector.

For more information on injectors you can visit the injectify.injectors module documentation.