AttributeError¶

The AttributeError is raised when there is a reference to a name that does not exist in an object that does exist. An attribute is a name for something that belongs to an object, for example, a human being has attributes like height, weight, sex and color.

test_attribute_error_w_variables ¶

red: make it fail¶

I open a terminal to run makePythonTdd.sh with attribute_error as the name of the project
```
./makePythonTdd.sh attribute_error
```
on Windows without Windows Subsystem Linux use makePythonTdd.ps1
```
./makePythonTdd.ps1 attribute_error
```
it makes the folders and files that are needed, installs packages, runs the first test, and the terminal shows AssertionError
```
E       AssertionError: True is not false

tests/test_attribute_error.py:7: AssertionError
```
I hold ctrl (windows/linux) or option (mac) on the keyboard and use the mouse to click on tests/test_attribute_error.py:7 to open it in the editor
then change True to False to make the test pass

I add an import statement

import unittest
import src.attribute_error

then change test_failure to test_attribute_error_w_variables
```
class TestAttributeError(unittest.TestCase):

    def test_attribute_error_w_variables(self):
        src.attribute_error.variable_00
```
I think of src.attribute_error.variable_00 as an address for variable_00 in attribute_error.py in the src folder, since the file is empty, the variable does not exist and the terminal shows AttributeError
```
AttributeError: module 'src.attribute_error' has no attribute 'variable_00'
```

I add the error to the list of Exceptions encountered

# Exceptions Encountered
# AssertionError
# AttributeError

green: make it pass¶

then I add a name to attribute_error.py

variable_00

which gives me NameError

NameError: name 'variable_00' is not defined

I add it to the list of Exceptions encountered

# Exceptions Encountered
# AssertionError
# AttributeError
# NameError

and point variable_00 to None
```
variable_00 = None
```
the test passes

refactor: make it better¶

I do it a few more times as a drill

def test_attribute_error_w_variables(self):
    src.attribute_error.variable_00
    src.attribute_error.variable_01

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'variable_01'. Did you mean: 'variable_00'?

I add the name to attribute_error.py

variable_00 = None
variable_01

and get NameError

NameError: name 'variable_01' is not defined

I point it to None

variable_00 = None
variable_01 = None

and the test passes

I do it again

def test_attribute_error_w_variables(self):
    src.attribute_error.variable_00
    src.attribute_error.variable_01
    src.attribute_error.variable_02

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'variable_02'. Did you mean: 'variable_00'?

I add the name and point it to None

variable_00 = None
variable_01 = None
variable_02 = None

and the terminal shows green again

one more time

def test_attribute_error_w_variables(self):
    src.attribute_error.variable_00
    src.attribute_error.variable_01
    src.attribute_error.variable_02
    src.attribute_error.variable_03

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'variable_03'. Did you mean: 'variable_00'?

I add it to the file

variable_00 = None
variable_01 = None
variable_02 = None
variable_03 = None

and the test passes

test_attribute_error_w_functions ¶

red: make it fail¶

I add a new test

def test_attribute_error_w_functions(self):
    src.attribute_error.function_00()

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'function_00'

green: make it pass¶

I add the name and point it to None

variable_00 = None
variable_01 = None
variable_02 = None
variable_03 = None


function_00 = None

the terminal shows TypeError

TypeError: 'NoneType' object is not callable

which I add to the list of Exceptions encountered

# Exceptions Encountered
# AssertionError
# AttributeError
# NameError
# TypeError

when I make it a function

variable_00 = None
variable_01 = None
variable_02 = None
variable_03 = None


def function_00():
    return None

the test passes

refactor: make it better¶

time to do it as a drill

def test_attribute_error_w_functions(self):
    src.attribute_error.function_00()
    src.attribute_error.function_01()

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'function_01'. Did you mean: 'function_00'?

I add the function to attribute_error.py

def function_00():
    return None


def function_01():
    return None

and the test passes

I add another line

def test_attribute_error_w_functions(self):
    src.attribute_error.function_00()
    src.attribute_error.function_01()
    src.attribute_error.function_02()

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'function_02'. Did you mean: 'function_00'?

I make the test pass

def function_00():
    return None


def function_01():
    return None


def function_02():
    return None

then I add another line

def test_attribute_error_w_functions(self):
    src.attribute_error.function_00()
    src.attribute_error.function_01()
    src.attribute_error.function_02()
    src.attribute_error.function_03()

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'function_03'. Did you mean: 'function_00'?

I add it to the module

def function_00():
    return None

def function_01():
    return None

def function_02():
    return None

def function_03():
    return None

and the test passes

test_attribute_error_w_class_attributes ¶

attributes are variables defined inside a class

red: make it fail¶

I add a new test

def test_attribute_error_w_class_attributes(self):
    src.attribute_error.AClass.attribute_00

the terminal shows AttributeError

AttributeError: module 'src.attribute_error' has no attribute 'AClass'

green: make it pass¶

I add it as a function

def function_00():
    return None

def function_01():
    return None

def function_02():
    return None

def function_03():
    return None

def AClass():
    return None

and the terminal shows AttributeError

AttributeError: 'function' object has no attribute 'attribute_00'

I define a variable in the function
```
def AClass():

    attribute_00 = None
    return None
```
and the terminal still shows the same exception because I cannot access a variable that belongs to a function from outside of it

I change the def keyword to the class keyword

class AClass():

    attribute_00 = None
    return None

and the terminal shows SyntaxError

E    return None
E    ^^^^^^^^^^^
E  SyntaxError: 'return' outside function

I add it to the list of Exceptions Encountered

# Exceptions Encountered
# AssertionError
# AttributeError
# NameError
# TypeError
# SyntaxError

then remove the return statement since AClass is no longer a function
```
class AClass():
    attribute_00 = None
```
and the test passes

refactor: make it better¶

I add another line

def test_attribute_error_w_class_attributes(self):
    src.attribute_error.AClass.attribute_00
    src.attribute_error.AClass.attribute_01

and the terminal shows AttributeError

AttributeError: type object 'AClass' has no attribute 'attribute_01'. Did you mean: 'attribute_00'?

I add the name to the class definition

class AClass():

    attribute_00 = None
    attribute_01 = None

and the test passes

I do it again

def test_attribute_error_w_class_attributes(self):
    src.attribute_error.AClass.attribute_00
    src.attribute_error.AClass.attribute_01
    src.attribute_error.AClass.attribute_02

the terminal shows AttributeError

 AttributeError: type object 'AClass' has no attribute 'attribute_02'. Did you mean: 'attribute_00'?

I make the test pass

class AClass():

    attribute_00 = None
    attribute_01 = None
    attribute_02 = None

then add one more line

def test_attribute_error_w_class_attributes(self):
    src.attribute_error.AClass.attribute_00
    src.attribute_error.AClass.attribute_01
    src.attribute_error.AClass.attribute_02
    src.attribute_error.AClass.attribute_03

and the terminal shows AttributeError

 AttributeError: type object 'AClass' has no attribute 'attribute_03'. Did you mean: 'attribute_00'?

I add the name

class AClass():

    attribute_00 = None
    attribute_01 = None
    attribute_02 = None
    attribute_03 = None

and the terminal shows passing tests

test_attribute_error_w_class_methods ¶

methods are functions defined inside a class

red: make it fail¶

I add a new test

def test_attribute_error_w_class_methods(self):
    src.attribute_error.AClass.method_00()

the terminal shows AttributeError

AttributeError: type object 'AClass' has no attribute 'method_00'

green: make it pass¶

I add the name to AClass and point it to None

class AClass():

    attribute_00 = None
    attribute_01 = None
    attribute_02 = None
    attribute_03 = None

    method_00 = None

and the terminal shows TypeError

TypeError: 'NoneType' object is not callable

I make it a method by using the def keyword to make it callable

class AClass():

    attribute_00 = None
    attribute_01 = None
    attribute_02 = None
    attribute_03 = None

    def method_00():
        return None

and the test passes

refactor: make it better¶

You know the “drill”, I add a new line

def test_attribute_error_w_class_methods(self):
    src.attribute_error.AClass.method_00()
    src.attribute_error.AClass.method_01()

the terminal shows AttributeError

AttributeError: type object 'AClass' has no attribute 'method_01'. Did you mean: 'method_00'?

I add a definition for it

class AClass():

    ...

    def method_00():
        return None

    def method_01():
        return None

and the terminal shows green again

I add another line

def test_attribute_error_w_class_methods(self):
    src.attribute_error.AClass.method_00()
    src.attribute_error.AClass.method_01()
    src.attribute_error.AClass.method_02()

the terminal shows AttributeError

AttributeError: type object 'AClass' has no attribute 'method_02'. Did you mean: 'method_00'?

I repeat the solution

class AClass():

    ...

    def method_00():
        return None

    def method_01():
        return None

    def method_02():
        return None

the test passes

then I add the last line

def test_attribute_error_w_class_methods(self):
    src.attribute_error.AClass.method_00()
    src.attribute_error.AClass.method_01()
    src.attribute_error.AClass.method_02()
    src.attribute_error.AClass.method_03()

and the terminal shows AttributeError

AttributeError: type object 'AClass' has no attribute 'method_03'. Did you mean: 'method_00'?

I make the test pass

class AClass():

    ...

    def method_00():
        return None

    def method_01():
        return None

    def method_02():
        return None

    def method_03():
        return None

review ¶

I ran tests for the AttributeError with

variables
functions
class attributes (variables)
class methods (functions)

I also ran into the following Exceptions

Would you like to test the TypeError?

AttributeError: tests and solutions

AttributeError¶

test_attribute_error_w_variables¶

red: make it fail¶

green: make it pass¶

refactor: make it better¶

test_attribute_error_w_functions¶

red: make it fail¶

green: make it pass¶

refactor: make it better¶

test_attribute_error_w_class_attributes¶

red: make it fail¶

green: make it pass¶

refactor: make it better¶

test_attribute_error_w_class_methods¶

red: make it fail¶

green: make it pass¶

refactor: make it better¶

review¶

test_attribute_error_w_variables ¶

test_attribute_error_w_functions ¶

test_attribute_error_w_class_attributes ¶

test_attribute_error_w_class_methods ¶

review ¶