Example:
import pytest
from app.objects
import Root # Example
known_links = [
"http://www.google.com",
"http://www.walla.com"
]
@pytest.fixture()
def root(request):
return Root() # Root object
@pytest.mark.parametrize("known_links", known_links)
def test_get_all_links_known_links(root, known_link):
html = Parser(
open(os.path.normpath(os.path.join(root, "test.html")))
)
assert any([known_link in str(l) for l in html.get_all_links()])You need to import parameterized before using the decorator:
from nose_parameterized
import parameterizedadd self. in front of html.get_all_links
self.assertTrue(any([known_link in str(l) for l in self.html.get_all_links()]))Pytest Test Class Calling Class Methods Type Error Takes Exactly 2 Arguments 1 Given, › Pytest test class calling class methods type error takes exactly 2 arguments 1 given ,I have a test class to test my methods but i have some issue with passing self, both of them are inside class and test class., This is a post to explain How To Fix Python TypeError – “Class Takes No Arguments (1 Given)”. This error occurs due to incorrect use of self parameter. The errors happens because the func () is a method within a Class.
def get_all_links(self): ""
"return all the links inside an html :return: list of links from an html page :rtype: list "
""
return self.html.find_all('a')import pytest from app.objects
import Root # Example known_links = ["http://www.google.com", "http://www.walla.com"] @pytest.fixture() def root(request): return Root() # Root object @pytest.mark.parametrize("known_links", known_links) def test_get_all_links_known_links(root, known_link): html = Parser(open(os.path.normpath(os.path.join(root, "test.html")))) assert any([known_link in str(l) for l in html.get_all_links()])def get_all_links(self): ""
"return all the links inside an html:return: list of links from an html page:rtype: list"
""
return self.html.find_all('a') @parameterized.expand(["http://www.google.com", "http://www.walla.com"]) def test_get_all_links_known_links(self, known_link): ""
"check get_all_links with a known link list :param known_link: lick to find :type known_link: str "
""
html = Parser(open(os.path.normpath(os.path.join(self.root, "test.html")))) self.assertTrue(any([known_link in str(l) for l in html.get_all_links()]))E TypeError: test_get_all_links_known_links() takes exactly 2 arguments(1 given) / usr / local / Cellar / python / 2.7 .9 / Frameworks / Python.framework / Versions / 2.7 / lib / python2 .7 / unittest /
case.py: 329: TypeError...import pytest from app.objects
import Root # Example known_links = ["http://www.google.com", "http://www.walla.com"] @pytest.fixture() def root(request): return Root() # Root object @pytest.mark.parametrize("known_links", known_links) def test_get_all_links_known_links(root, known_link): html = Parser(open(os.path.normpath(os.path.join(root, "test.html")))) assert any([known_link in str(l) for l in html.get_all_links()])Last updated: Apr 20, 2022
Copied!class Employee():
#👇️ forgot to take self arg
def get_name():
return 'Alice'
emp = Employee()
#⛔️ TypeError: Employee.get_name() takes 0 positional arguments but 1 was given
print(emp.get_name())Copied!class Employee():
#👇️ specify self arg
def get_name(self):
return 'Alice'
emp = Employee()
print(emp.get_name()) #👉️ "Alice"Copied!class Employee():
@staticmethod
def get_name():
return 'Alice'
emp = Employee()
print(emp.get_name()) #👉️ "Alice"Copied!def get_list():
return ['a', 'b', 'c']
#⛔️ TypeError: get_list() takes 0 positional arguments but 1 was given
result = get_list('a')Copied!def get_list():
return ['a', 'b', 'c']
result = get_list()
print(result) #👉️['a', 'b', 'c']Copied!def get_list(x):
return ['a', 'b', 'c', x]
result = get_list('d')
print(result) #👉️['a', 'b', 'c', 'd']In this article, we’ll learn how to fix the error “Takes 0 positional arguments but 1 was given”. Let’s get started!,In the above case, the divide() function requires two parameters. Both the parameters are mandatory and neither of them is positional. This is why, the function throws an error “takes 0 positional arguments, but 1 was given”,The topic of “takes 0 positional arguments but 1 was given” ends here. The concept is straightforward. I hope you were able to fix the error in your code. IF you have any questions, drop us a line and we’ll help you out.,Now when we need to add two numbers, we only need to pass those numbers as arguments to the function. Take a look below:
def add_numbers(num_1, num_2):
sum = num_1 + num_2
print('The sum of two numbers is: ', sum)>>> add_numbers(33, 23) # calling the
function first time
>>>
The sum of two numbers is: 56 >>>
add_numbers(45, 45) # calling the
function second time
>>>
The sum of two numbers is: 90def multiply(num_1, num_2):
product = num_1 * num_2
print('The product of two numbers is: ', product)>>> multiply(4, 100) # calling the
function first time
>>>
The product of two numbers is: 400 >>>
multiply(40, 60) # calling the
function second time
>>>
The product of two numbers is: 2400Traceback (most recent call last):
File "c:\Users\Lenovo\Desktop\sample.py", line 8, in <module>
function(parameter)
TypeError: function() takes 0 positional arguments but 1 was givendef divide():
num_1 = int(input('enter num_1: ')) # taking input
for num_1
num_2 = int(input('enter num_2: ')) # taking input
for num_2
div = num1 / num2
print('The division is: ', div)
divide(3)The error says that as per the definition of method, it accepts no arguments, but we provided an an argument.,And to comply this inbuilt behavior, we need to provide an argument in the definition of details() method as shown below:,In this tutorial of Python Examples, we have learned to solve the TypeError: method() takes 0 positional arguments but 1 was given, with the help of example programs.,You might be wondering that you have not passed any arguments when you called details() method on the laptop1 object. But, why Python is throwing the TypeError?
Python Program
class Laptop:
def details():
print('Hello! I am a laptop.')
laptop1 = Laptop()
laptop1.details()Output
Traceback (most recent call last):
File "example1.py", line 6, in <module>
laptop1.details()
TypeError: details() takes 0 positional arguments but 1 was givenMock supports the mocking of Python magic methods. The easiest way of using magic methods is with the MagicMock class. It allows you to do things like:,The following is an example of using magic methods with the ordinary Mock class:,Mock allows you to assign functions (or other Mock instances) to magic methods and they will be called appropriately. The MagicMock class is just a Mock variant that has all of the magic methods pre-created for you (well, all the useful ones anyway).,The Mock classes have support for mocking magic methods. See magic methods for the full details.
>>> from unittest.mock
import MagicMock
>>>
thing = ProductionClass() >>>
thing.method = MagicMock(return_value = 3) >>>
thing.method(3, 4, 5, key = 'value')
3
>>>
thing.method.assert_called_with(3, 4, 5, key = 'value')>>> mock = Mock(side_effect = KeyError('foo')) >>>
mock()
Traceback(most recent call last):
...
KeyError: 'foo'>>> values = {
'a': 1,
'b': 2,
'c': 3
} >>>
def side_effect(arg):
...
return values[arg]
...
>>>
mock.side_effect = side_effect >>>
mock('a'), mock('b'), mock('c')
(1, 2, 3) >>>
mock.side_effect = [5, 4, 3, 2, 1] >>>
mock(), mock(), mock()
(5, 4, 3)>>> from unittest.mock
import patch
>>>
@patch('module.ClassName2')
...@patch('module.ClassName1')
...def test(MockClass1, MockClass2):
...module.ClassName1()
...module.ClassName2()
...assert MockClass1 is module.ClassName1
...assert MockClass2 is module.ClassName2
...assert MockClass1.called
...assert MockClass2.called
...
>>>
test()>>> with patch.object(ProductionClass, 'method', return_value = None) as mock_method:
...thing = ProductionClass()
...thing.method(1, 2, 3)
...
>>>
mock_method.assert_called_once_with(1, 2, 3)>>> foo = {
'key': 'value'
} >>>
original = foo.copy() >>>
with patch.dict(foo, {
'newkey': 'newvalue'
}, clear = True):
...assert foo == {
'newkey': 'newvalue'
}
...
>>>
assert foo == originalIf you instantiate an object of a class but use incorrect syntax, you can also raise the “missing 1 required positional argument: ‘self’” error. Let’s look at the following example:,You must instantiate an object of the class before calling a class method; otherwise, self will have no value. We can only call a method using the class object and not the class name. Therefore we also need to use the correct syntax of parentheses after the class name when instantiating an object.,Congratulations on reading to the end of this tutorial. The error “missing 1 required argument: ‘self'” occurs when you do not instantiate an object of a class before calling a class method. You can also raise this error if you use incorrect syntax to instantiate a class. To solve this error, ensure you instantiate an object of a class before accessing any of the class’ methods. Also, ensure you use the correct syntax when instantiating an object and remember to use parentheses when needed. ,We can think of a class as a blueprint for objects. All of the functionalities within the class are accessible when we instantiate an object of the class.
This example will define a class that stores information about particles. We will add a function to the class. Functions within classes are called methods, and the method show_particle prints the name of the particle and its charge.
class Particle:
def __init__(self, name, charge):
self.name = name
self.charge = charge
def show_particle(self):
print(f 'The particle {self.name} has a charge of {self.charge}')Let’s try to create an object and assign it to the variable muon. We can derive the muon object from the Particle class, and therefore, it has access to the Particle methods. Let’s see what happens when we call the show_particle() method to display the particle information for the muon.
muon = Particle.show_particle()
muon = Particle.show_particle()
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -
TypeError Traceback(most recent call last)
muon = Particle.show_particle()
TypeError: show_particle() missing 1 required positional argument: 'self'If we run the code, we will get the particle information successfully printed out. This version of the code works because we first declared a variable muon, which stores the information about the particle Muon. The particle Muon has a charge of -1. Once we have an instantiated object, we can call the show_particle() method.
The particle Muon has a charge of -1If you instantiate an object of a class but use incorrect syntax, you can also raise the “missing 1 required positional argument: ‘self’” error. Let’s look at the following example:
proton = Particle proton.show_particle()
At a basic level, test functions request fixtures they require by declaring them as arguments.,Tests and fixtures aren’t limited to requesting a single fixture at a time. They can request as many as they like. Here’s another quick example to demonstrate:,Notice that the methods are only referencing self in the signature as a formality. No state is tied to the actual test class as it might be in the unittest.TestCase framework. Everything is managed by the pytest fixture system.,While yield fixtures are considered to be the cleaner and more straightforward option, there is another choice, and that is to add “finalizer” functions directly to the test’s request-context object. It brings a similar result as yield fixtures, but requires a bit more verbosity.
import pytest
class Fruit:
def __init__(self, name):
self.name = name
self.cubed = False
def cube(self):
self.cubed = True
class FruitSalad:
def __init__(self, * fruit_bowl):
self.fruit = fruit_bowl
self._cube_fruit()
def _cube_fruit(self):
for fruit in self.fruit:
fruit.cube()
# Arrange
@pytest.fixture
def fruit_bowl():
return [Fruit("apple"), Fruit("banana")]
def test_fruit_salad(fruit_bowl):
# Act
fruit_salad = FruitSalad( * fruit_bowl)
# Assert
assert all(fruit.cubed
for fruit in fruit_salad.fruit)def fruit_bowl():
return [Fruit("apple"), Fruit("banana")]
def test_fruit_salad(fruit_bowl):
# Act
fruit_salad = FruitSalad( * fruit_bowl)
# Assert
assert all(fruit.cubed
for fruit in fruit_salad.fruit)
# Arrange
bowl = fruit_bowl()
test_fruit_salad(fruit_bowl = bowl)# contents of test_append.py
import pytest
# Arrange
@pytest.fixture
def first_entry():
return "a"
# Arrange
@pytest.fixture
def order(first_entry):
return [first_entry]
def test_string(order):
# Act
order.append("b")
# Assert
assert order == ["a", "b"]def first_entry():
return "a"
def order(first_entry):
return [first_entry]
def test_string(order):
# Act
order.append("b")
# Assert
assert order == ["a", "b"]
entry = first_entry()
the_list = order(first_entry = entry)
test_string(order = the_list)# contents of test_append.py
import pytest
# Arrange
@pytest.fixture
def first_entry():
return "a"
# Arrange
@pytest.fixture
def order(first_entry):
return [first_entry]
def test_string(order):
# Act
order.append("b")
# Assert
assert order == ["a", "b"]
def test_int(order):
# Act
order.append(2)
# Assert
assert order == ["a", 2]def first_entry():
return "a"
def order(first_entry):
return [first_entry]
def test_string(order):
# Act
order.append("b")
# Assert
assert order == ["a", "b"]
def test_int(order):
# Act
order.append(2)
# Assert
assert order == ["a", 2]
entry = first_entry()
the_list = order(first_entry = entry)
test_string(order = the_list)
entry = first_entry()
the_list = order(first_entry = entry)
test_int(order = the_list)