Consider the naming convention used for different types of containers in the Python standard library:
Why do some methods follow camel case, but others like deque and defaultdict don't? How are these methods different from each other in a way that would explain this difference?
If it's because at some point the convention changed, why wouldn't the module e.g. provide alias them with camel case names to old names as well?
Usually in python, class names follow the "pascal" case convention, methods / functions follow the "snake" case convention.
But here is a official reference from https://www.python.org/dev/peps/pep-0008/:
Package and Module Names
Modules should have short, all-lowercase
names. Underscores can be used in the module name if it improves
readability. Python packages should also have short, all-lowercase
names, although the use of underscores is discouraged.
When an extension module written in C or C++ has an accompanying
Python module that provides a higher level (e.g. more object oriented)
interface, the C/C++ module has a leading underscore (e.g. _socket).
Class names
Class names should normally use the CapWords convention.
The naming convention for functions may be used instead in cases where
the interface is documented and used primarily as a callable.
Note that there is a separate convention for builtin names: most
builtin names are single words (or two words run together), with the
CapWords convention used only for exception names and builtin
constants.
I am creating a UML diagram for a Python class.
Is it standard to include the public/private/protected tags when doing UMLs for Python programs? For instance:
-n: int
+name_of_shop: str
My current program has every variable and function as public, since I didn't want my variables to start with single (_) or double (__) underscores. If the variables aren't accessed outside the function, is it standard for every variable to begin with the double underscore?
There is no Python standard vis-a-vis UML. There are conventions in both paradigms. How you resolve them is up to you and your consumers, i.e., whomever is evaluating your work.
Python itself imposes very few standards beyond the necessity of the language syntax. Remember our over-arching precept: "A Foolish Consistency is the Hobgoblin of Little Minds". You can see the coding guidelines (often referred to as The PEP-8 Coding Standard").
That said, I have two basic notes:
Yes, internal variables generally begin with an underscore.
You need to take up the readability and propriety with your instructor and/or grader.
If your question is whether to use underscore, PEP8 has it
Descriptive: Naming Styles
Basically says
_single underscore prefix for weak "internal use" indicator
single_ underscore suffix for avoiding conflicts with keyword
__double underscore prefix for mangles
__ double__ underscore on both end for magic that should not be invented.
The norm for Python standard library classes seems to be that class names are lowercase - this appears to hold true for built-ins such as str and int as well as for most classes that are part of standard library modules that must be imported such as datetime.date or datetime.datetime.
But, certain standard library classes such as enum.Enum and decimal.Decimal are capitalized. At first glance, it might seem that classes are capitalized when their name is equal to the module name, but that does not hold true in all cases (such as datetime.datetime).
What's the rationale/logic behind the capitalization conventions for class names in the Python Standard Library?
The Key Resources section of the Developers Guide lists PEP 8 as the style guide.
From PEP 8 Naming Conventions, emphasis mine.
The naming conventions of Python's library are a bit of a mess, so
we'll never get this completely consistent -- nevertheless, here are
the currently recommended naming standards. New modules and packages
(including third party frameworks) should be written to these
standards, but where an existing library has a different style,
internal consistency is preferred.
Also from PEP 8
A style guide is about consistency. Consistency with this style guide
is important. Consistency within a project is more important.
Consistency within one module or function is the most important.
...
Some other good reasons to ignore a particular guideline:
To be consistent with surrounding code that also breaks it (maybe for historic reasons) -- although this is also an opportunity to clean
up someone else's mess (in true XP style).
Because the code in question predates the introduction of the guideline and there is no other reason to be modifying that code.
You probably will never know why Standard Library naming conventions conflict with PEP 8 but it is probably a good idea to follow it for new stuff or even in your own projects.
Pep 8 is considered to be the standard style guide by many Python devs. This recommends to name classes using CamelCase/CapWords.
The naming convention for functions may be used instead in cases where the interface is documented and used primarily as a callable.
Note that there is a separate convention for builtin names: most builtin names are single words (or two words run together), with the CapWords convention used only for exception names and builtin constants.
Check this link for PEP8 naming conventions and standards.
datetime is a part of standard library,
Python’s standard library is very extensive, offering a wide range of facilities as indicated by the long table of contents listed below. The library contains built-in modules (written in C) that provide access to system functionality such as file I/O that would otherwise be inaccessible to Python programmers, as well as modules written in Python that provide standardized solutions for many problems that occur in everyday programming.
In some cases, like sklearn, nltk, django, the package names are all lowercase. This link will take you there.
Modules should have short, all-lowercase names. Underscores can be used in the module name if it improves readability. Python packages should also have short, all-lowercase names, although the use of underscores is discouraged.
When an extension module written in C or C++ has an accompanying Python module that provides a higher level (e.g. more object oriented) interface, the C/C++ module has a leading underscore (e.g. _socket ).
I hope this covers all the questions.
I'm using Python, but I think it's same for pretty much every programming languages. It has nothing to do with the functionalities, but I came to notice that when I see other people's codes, variable names with multiple words are connected, and the first letters of each words (except for the first one) are capitalized.
thisIsATypicalVariableNameWithMultipleWords = 0
But when using functions, usually nothing is capitalized and the words are connected by _.
this_is_a_typical_function_name_with_multiple_words()
Is this how the variables and functions are typically named? Thanks in advance.
You are looking at a naming convention, and such conventions are rather arbitrary but usually agreed upon in a style guide.
The Python developers have published such a style guide for Python: PEP 8 -- Style Guide for Python Code. It includes a section on naming conventions for Python code. You don't have to adhere to these, but it is a good idea to do so if you want to work with other Python developers where most do adhere to these conventions.
The style guide also provides you with names for the styles; your two specific styles (which are not the only two styles), are called mixedCase and lower_case_with_underscores.
mixedCase is no longer used in Python code; the style guide only mentions it as a legacy case for function names used by certain older standard library modules.
lower_case_with_underscores is the current recommended convention for function, method and attribute names.
Coming from a C# background the naming convention for variables and method names are usually either camelCase or PascalCase:
// C# example
string thisIsMyVariable = "a"
public void ThisIsMyMethod()
In Python, I have seen the above but I have also seen underscores being used:
# python example
this_is_my_variable = 'a'
def this_is_my_function():
Is there a more preferable, definitive coding style for Python?
See Python PEP 8: Function and Variable Names:
Function names should be lowercase, with words separated by underscores as necessary to improve readability.
Variable names follow the same convention as function names.
mixedCase is allowed only in contexts where that's already the prevailing style (e.g. threading.py), to retain backwards compatibility.
The Google Python Style Guide has the following convention:
module_name, package_name, ClassName, method_name, ExceptionName, function_name, GLOBAL_CONSTANT_NAME, global_var_name, instance_var_name, function_parameter_name, local_var_name.
A similar naming scheme should be applied to a CLASS_CONSTANT_NAME
David Goodger (in "Code Like a Pythonista" here) describes the PEP 8 recommendations as follows:
joined_lower for functions, methods,
attributes, variables
joined_lower or ALL_CAPS for
constants
StudlyCaps for classes
camelCase only to conform to
pre-existing conventions
As the Style Guide for Python Code admits,
The naming conventions of Python's
library are a bit of a mess, so we'll
never get this completely consistent
Note that this refers just to Python's standard library. If they can't get that consistent, then there hardly is much hope of having a generally-adhered-to convention for all Python code, is there?
From that, and the discussion here, I would deduce that it's not a horrible sin if one keeps using e.g. Java's or C#'s (clear and well-established) naming conventions for variables and functions when crossing over to Python. Keeping in mind, of course, that it is best to abide with whatever the prevailing style for a codebase / project / team happens to be. As the Python Style Guide points out, internal consistency matters most.
Feel free to dismiss me as a heretic. :-) Like the OP, I'm not a "Pythonista", not yet anyway.
As mentioned, PEP 8 says to use lower_case_with_underscores for variables, methods and functions.
I prefer using lower_case_with_underscores for variables and mixedCase for methods and functions makes the code more explicit and readable. Thus following the Zen of Python's "explicit is better than implicit" and "Readability counts"
There is PEP 8, as other answers show, but PEP 8 is only the styleguide for the standard library, and it's only taken as gospel therein. One of the most frequent deviations of PEP 8 for other pieces of code is the variable naming, specifically for methods. There is no single predominate style, although considering the volume of code that uses mixedCase, if one were to make a strict census one would probably end up with a version of PEP 8 with mixedCase. There is little other deviation from PEP 8 that is quite as common.
further to what #JohnTESlade has answered. Google's python style guide has some pretty neat recommendations,
Names to Avoid
single character names except for counters or iterators
dashes (-) in any package/module name
\__double_leading_and_trailing_underscore__ names (reserved by Python)
Naming Convention
"Internal" means internal to a module or protected or private within a class.
Prepending a single underscore (_) has some support for protecting module variables and functions (not included with import * from). Prepending a double underscore (__) to an instance variable or method effectively serves to make the variable or method private to its class (using name mangling).
Place related classes and top-level functions together in a module. Unlike Java, there is no need to limit yourself to one class per module.
Use CapWords for class names, but lower_with_under.py for module names. Although there are many existing modules named CapWords.py, this is now discouraged because it's confusing when the module happens to be named after a class. ("wait -- did I write import StringIO or from StringIO import StringIO?")
Guidelines derived from Guido's Recommendations
Most python people prefer underscores, but even I am using python since more than 5 years right now, I still do not like them. They just look ugly to me, but maybe that's all the Java in my head.
I simply like CamelCase better since it fits better with the way classes are named, It feels more logical to have SomeClass.doSomething() than SomeClass.do_something(). If you look around in the global module index in python, you will find both, which is due to the fact that it's a collection of libraries from various sources that grew overtime and not something that was developed by one company like Sun with strict coding rules. I would say the bottom line is: Use whatever you like better, it's just a question of personal taste.
Personally I try to use CamelCase for classes, mixedCase methods and functions. Variables are usually underscore separated (when I can remember). This way I can tell at a glance what exactly I'm calling, rather than everything looking the same.
There is a paper about this: http://www.cs.kent.edu/~jmaletic/papers/ICPC2010-CamelCaseUnderScoreClouds.pdf
TL;DR It says that snake_case is more readable than camelCase. That's why modern languages use (or should use) snake wherever they can.
The coding style is usually part of an organization's internal policy/convention standards, but I think in general, the all_lower_case_underscore_separator style (also called snake_case) is most common in python.
I personally use Java's naming conventions when developing in other programming languages as it is consistent and easy to follow. That way I am not continuously struggling over what conventions to use which shouldn't be the hardest part of my project!
Whether or not being in class or out of class:
A variable and function are lowercase as shown below:
name = "John"
def display(name):
print("John")
And if they're more than one word, they're separated with underscore "_" as shown below:
first_name = "John"
def display_first_name(first_name):
print(first_name)
And, if a variable is a constant, it's uppercase as shown below:
FIRST_NAME = "John"
Lenin has told... I'm from Java/C# world too. And SQL as well.
Scrutinized myself in attempts to find first sight understandable examples of complex constructions like list in the dictionary of lists where everything is an object.
As for me - camelCase or their variants should become standard for any language. Underscores should be preserved for complex sentences.
Typically, one follow the conventions used in the language's standard library.