Sourcery Tutorial

To check Sourcery is working, copy the code below into your editor then look for the underlined if a: in the function below. If you hover over it you should see a diff, with Sourcery suggesting the merge-nested-ifs refactoring. All of the suggestions Sourcery has found will also appear in the Problems pane.

def merge_nested_if(a, b):
    if a:
        if b:
            return c

If you take the quick fix action to merge nested if conditions suggested on the code above you should end up with the code below:

def merge_nested_if(a, b):
    if a and b:
        return c

Here are some more examples of what Sourcery can do. Copy them into your code editor to see what it suggests:

def list_comprehension(list, filter, func):
    new_list = list()
    for i in list:
        if filter(i):
            new_list.append(func(i))
    return new_list


def augmented_assignment():
    a = 0
    a = a + 1
    print(a)


def sort_out_return():
    if something == other_thing:
        return True
    return False


def dictionary_get():
    dictionary = {}
    data = ""
    if "message" in dictionary:
        data = dictionary["message"]

And here Sourcery is chaining together several changes to make a larger one

def enable_local(self, opt):
  if opt == ECHO:
    return True
  elif opt == SGA:
    return True
  else:
    return False


def __getstate__(self):
  state = {}
  state['min'] = self.min
  state['max'] = self.max
  return state

This method has been commented to skip a specific refactoring. If you remove the comment Sourcery will suggest the use-any refactoring.

def convert_to_any(): # sourcery skip: use-any
    found = False
    for thing in things:
        if do_something_serious(thing):
            found = True
            break

There are quick fix actions to skip the specific suggestions or all suggestions. You can also turn off refactorings globally through adding a .sourcery.yaml file to the root of your project using the following settings:

# Refactoring config
refactor:
  # Refactoring ids to skip
  #
  # These refactorings will never be suggested by Sourcery
  skip:
    - use-any

Sourcery will not make a refactoring if it would mean removing a comment. Remove the comment in the method below to see what happens!

def count_sheeps(arrayOfSheeps):
  num_of_sheep = 0 # Remove this comment!
  for i in range(len(arrayOfSheeps)):
    if arrayOfSheeps[i] == True:
      num_of_sheep += 1
  return num_of_sheep

We also show code metrics right in the IDE

Just hover over the line where a function is defined to get a view of its complexity, length, working memory usage and the overall quality score.

These metrics can be switched off in the Sourcery configuration for VS Code and PyCharm.

Here's an intentionally low quality function which is flagged as a warning:

def example_function(condition, other_condition, third_condition, delimiter, extra_var):
    if condition:
        if other_condition and third_condition:
            seen = set()
            for (s, nbrs) in G.adjacency_iter:
                nbr_edges = [
                    (u, data)
                    for (u, datadict) in nbrs.items()
                    if u not in seen
                    for (key, data) in datadict.items()
                ]
                deg = len(nbr_edges)
                yield make_str(s) + delimiter + "%i" % deg
                for (u, d) in nbr_edges:
                    if is_valid(u):
                        if d is None:
                            yield make_str(u)
                        else:
                            yield make_str(u) + delimiter + make_str(d)
                seen.add(s)
    else:
        if other_condition and third_condition:
            seen = set()
            for (s, nbrs) in G.adjacency_iter:
                nbr_edges = [(u, d) for (u, d) in nbrs.items() if u not in seen]
                deg = len(nbr_edges)
                yield make_str(s) + delimiter + "%i" % deg
                for (u, d) in nbr_edges:
                    if is_valid(u):
                        if d is None:
                            yield make_str(u)
                        else:
                            yield make_str(u) + delimiter + make_str(d)
                seen.add(s)
    return Edges(seen, extra_var)

The threshold at which a low quality score shows up as a warning is set at 25% by default. This can be altered on a project-by-project basis. Just add the config below to your .sourcery.yaml file.

# Code Metrics configuration
metrics:
  # These are shown at the method level when hovering the mouse
  # over the method name.
  #
  # The quality score is a percentage.
  #
  # Methods with a quality lower than this threshold will be flagged
  # as warnings. The default threshold is 25.0
  #
  quality_threshold: 25.0