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Fluentcheck

Fluent assertion framework for Python

Bored of using assert multiple times to check types, intervals, etc. on data passed as input to your Python functions? This generates a lot of boilerplate code.

fluentcheck helps you reducing the lines of code providing a human-friendly and fluent way to make assertions.

Instead of:

def my_function(n, obj):
    assert n is not None
    assert isinstance(n, float)
    assert 0. < n < 1.
    assert obj is not None
    assert isinstance(obj, MyCustomType)

you just streamline the assertions ("checks") you want to make, in a fluent way:

from fluentcheck import Check

def my_function(n, obj):
    Check(n).is_not_None().is_float().is_between(0., 1.)
    Check(obj).is_not_None().is_subtype_of(MyCustomType)

You can even use the alternate Is syntax:

from fluentcheck import Is

def my_function(n, obj):
    Is(n).not_none.float.between(0, 1)
    Is(obj).not_none.subtype_of(MyCustomType)

Fluentcheck can also be used as an assertion framework in tests.

Installation

pip install fluentcheck

or

python setup.py install

Only Python 3 is supported (because you DID update your code to Python3, didn't you?)

Usage

Check API

Simply instantiate the Check wrapper around the Python value you want to check out, then fluently append assertions like this:

from fluentcheck import Check

Check(my_value).assertion1().assertion2().assertion3() # and so on

Is API

Simply instantiate the Is wrapper around the Python value you want to check out, then fluently append assertions like this:

from fluentcheck import Is

Is(my_value).assertion1.assertion2_with_params(a, b).assertion3 # and so on

When an assertion fails

What if an assertion fails? A CheckError is raised: just catch it!

Please notice: if the order of assertions matters to your overall goal, then take care of it!

Linters and Is API

You may run into warnings for code such as this when using the Is API:

n = .4
Is(n).not_none.float.non_negative

# WARNING: Statement seems to have no effect ...

While not required for assertions to work, you can always "call" the last assertion to make linters happy:

n = .4
Is(n).not_none.float.non_negative()

# Happy, calling non_negative() has no effect but the linter warnings are gone.

What can I actually check with it?

To date, here's a list of assertions you can make:

Check API

# Check(value).X where X is one of:

# Numbers
is_none()
is_not_none()
is_number()
is_not_number()
is_integer()
is_not_integer()
is_long()
is_not_long()
is_float()
is_not_float()
is_real()
is_not_real()
is_complex()
is_not_complex()
is_positive()
is_not_positive()
is_negative()
is_not_negative()
is_zero()
is_not_zero()
is_at_least(lower)
is_at_most(upper)
is_between(lower, upper)
is_not_between(lower, upper)

# Sequences
is_empty()
is_not_empty()
is_iterable()
is_not_iterable()
is_couple()
is_triplet()
is_nuple(dimension)
has_dimensionality(dimensionality)

# Tuples
is_tuple()

# Lists
is_list()

# Strings
is_string()
is_not_string()
contains_numbers()
not_contains_numbers()
contains_numbers_only()
contains_chars()
not_contains_chars()
contains_chars_only()
contains_spaces()
not_contains_spaces()
contains_char(_char)
not_contains_char(_char)
is_shorter_than(n_chars)
is_longer_than(n_chars)
has_length(n_chars)
has_not_length(n_chars)
is_lowercase()
is_not_lowercase()
is_uppercase()
is_not_uppercase()
is_camelcase()
is_not_camelcase()
is_snakecase()
is_not_snakecase()
is_unicode()
is_not_unicode()
is_json()
is_not_json()
is_yaml()
is_not_yaml()
is_xml()
is_not_xml()
matches(regex)
not_matches(regex)

# Booleans
is_boolean()
is_not_boolean()
is_true()
is_not_true()
is_truthy()
is_not_truthy()
is_false()
is_not_false()
is_falsy()
is_not_falsy()
has_same_truth_of(val)
has_opposite_truth_of(val)

# Dictionaries
is_dict()
is_not_dict()
has_keys(*args)
has_not_keys(*args)

# Sets
is_set()
is_not_set()
is_subset_of(_set)
is_not_subset_of(_set)
is_superset_of(_set)
is_not_superset_of(_set)
intersects(_set)
not_intersects(_set)

# Functions
is_runnable()
is_not_runnable()

# Modules
is_module()
is_not_module()

# Type hierarchy
is_subtype_of(_type)
is_not_subtype_of(_type)

# Custom types
is_of_type(_type)
is_not_of_type(_type)

# Geographic coords
is_latitude()
is_longitude()
is_azimuth()
is_geopoint()

# UUIDs
is_uuid1()
is_not_uuid1()
is_uuid4()
is_not_uuid4()

Is API

# Is(value).X where X is one of:

# Numbers
none
not_none
number
not_number
integer
not_integer
float
not_float
real
not_real
complex
not_complex
positive
not_positive
negative
not_negative
zero
not_zero
at_least(lower)
at_most(upper)
between(lower, upper)
not_between(lower, upper)

# Sequences
empty
not_empty
iterable
not_iterable
has_dimensionality(dimensionality)

# Tuples
tuple

# Lists
list

# Strings
string
not_string
contains_numbers
not_contains_numbers
only_numbers
contains_chars
not_contains_chars
only_chars
contains_spaces
not_contains_spaces
contains_char(_char)
not_contains_char(_char)
shorter_than(n_chars)
longer_than(n_chars)
length(n_chars)
not_length(n_chars)

json
not_json
matches(regex)
not_matches(regex)

# Booleans
boolean
not_boolean
true
not_true
truthy
not_truthy
false
not_false
falsy
not_falsy
has_same_truth_of(val)
has_opposite_truth_of(val)

# Dictionaries
dict
not_dict
has_keys(*args)
has_not_keys(*args)

# Sets
set
not_set
subset_of(_set)
not_subset_of(_set)
superset_of(_set)
not_superset_of(_set)
intersects(_set)
not_intersects(_set)

# Type hierarchy
subtype_of(_type)
not_subtype_of(_type)

# UUIDs
is_uuid1()
is_not_uuid1()
is_uuid4()
is_not_uuid4()

Coming soon

The following checks will be added in the upcoming versions:

# Dates
is_date()
is_not_date()
is_datetime()
is_not_datetime()
is_before(_datetime)
is_not_before(_datetime)
is_after(_datetime)
is_not_after(_datetime)
is_today()
is_not_today()
is_yesterday()
is_not_yesterday()
is_tomorrow()
is_not_tomorrow()
is_weekend()
is_not_weekend()
is_this_month()
is_not_this_month()
is_previous_month()
is_not_previous_month()
is_next_month()
is_not_next_month()
is_this_year()
is_not_this_year()
is_last_year()
is_not_last_year()
is_next_year()
is_not_next_year()
is_leap_year()
is_not_leap_year()
is_this_century()
is_not_this_century()
is_before(date)
is_not_before(date)
is_after(date)
is_not_after(date)
is_between_dates(lower, upper)
is_not_between_dates(lower, upper)
is_timezone_aware()
is_not_timezone_aware()
has_timezone(tz)
has_not_timezone(tz)

# Geographic coords
is_plus_code()  # https://plus.codes/
is_not_plus_code()

# Check against a custom rule (lambda)
conforms_to(func)
not_conforms_to(func)

# Sequences
is_sorted(rule=func)
is_not_sorted(rule=func)
is_subsequence_of(subseq)
is_not_subsequence_of(subseq)
has_duplicates()
has_not_duplicates()

# Objects
contains(element)
not_contains(element)
has_attribute(_attr)
has_not_attribute(_attr)

License

MIT license