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author ： Test caituotuo
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Hello everyone , I'm testing caituotuo .
today , Let's talk Python Name those things .
It is called the beginning of all things , All things begin without name , Dao begets One , One begets Two , Two begets Three , Our vision-be .
“ How to name variables ？” It seems to be a very basic content , But there are still many people who are a little confused in this part .
Naming is often considered a detail in programming , Its importance is often underestimated . And the so-called craftsman spirit , Often reflected in the details .
Programmers have... In their work 80% Time spent reading and understanding code , Good naming can improve the readability and expressiveness of the code , Names that don't convey the meaning of words can be confusing , Add unnecessary thought overhead .
Learn from good examples Python, Start with variable naming .
What is a legal variable name ？
The so-called legal variable name is Python Variable names that the interpreter can recognize .
It is also a rule that must be followed in the coding process , Suppose you don't follow the rules , The program will report an error .
stay Python in , A valid variable name is given by Letter 、 Underline and Numbers form , And the first character cannot be a number .
stay Python3 in , The definition of letters is actually broad , You can write a Chinese variable name , In other words, you can think that the Chinese word is also a kind of letter , However, it is generally not recommended to use Chinese variable names , Because sometimes there may be some inexplicable... Due to some coding reasons bug.
caituotuo_666 = " Test caituotuo " # √
# 666caituotuo_666 = " Test caituotuo " # × The beginning of the number is illegal
Cai Tuotuo = " Test caituotuo " # √ Not recommended
Legal variable names obviously give us a lot of room to operate , We can take a variety of variables 、 Strange names .
What is a good variable name ？
A good variable name is a kind of Naming specification , Although the naming convention is not followed , The program can still run , However, using naming conventions can more intuitively understand the meaning of the code , So with Python It is important that developers use the same naming system .
We can judge the quality of a variable name from its content and form .
From the perspective of content, it is how much effective information this variable name passes , Whether it is a meaningful variable name . Meaningful variable names can achieve the effect that the code is the document , High readability , There is no need for comments and documentation , The code itself can express the developer's intention explicitly .
For example, the following three variables ：
n = " Test caituotuo "
name = " Test caituotuo "
username = " Test caituotuo "
however , The more effective information, the better , Obviously not , We also need to make a trade-off between valid information and variable name length （ The balance between the two depends on the project itself and the accumulation of experience ）, Variable names should not be rounded to infinity in order to show more information , It is not an inch long and an inch strong , For example, the following variable name is too long
student_system_login_username = " Test caituotuo "
During coding , A variable name sometimes requires two or more words , When these words are crowded together , It's hard to tell who is who . So formally, we have four different ways to write variable names ：
lower_underscore = " Test caituotuo "
UPPER_UNDERSCORE = " Test caituotuo "
CamelCase = " Test caituotuo "
mixedCase = " Test caituotuo "
Naming Convention Naming specification
stay PEP8 There are more detailed descriptions in it , Original address ：https://peps.python.org/pep-0008/#naming-conventions
Naming Convention The core of consistency（ Uniformity ）
The official meaning is probably ：
When you see a variable name , How to quickly identify variables or Constant or class or function or …？
You need consistency , In other words, good variables don't just make your program look good , At the same time, it can also improve the programming efficiency .
stay Python There are three formats used in ：lower_underscore、UPPER_UNDERSCORE、CamelCase, It won't use mixedCase.
lower_underscore： Lowercase letters followed by underscores （ Except constants and class names , All remaining names are lowercase underscores , Include ：module modular 、variable Variable 、function function 、method Method , They are Python Is usually used as a variable 、 Delivered , So they are named in the same way ）
UPPER_UNDERSCORE： Capital letters followed by underscores , Only used to express Constant （ Actually in Python There are no real constants in , More is a kind of agreement , You don't move and I don't move , So when you want to express constants, you can use uppercase underscores , At the same time Python In the standard library, when you see the uppercase underline, you know that it is a constant ）
CamelCase： The big hump in Hump naming , Distinguish words by capitalization , Only used to express class
mixedCase： The small hump in the name of hump , The difference with the big hump is that the first letter is lowercase （ Not in Python Use in ）
_stay Python Interpreter , There is a special feeling for single underscores .
Single underscores are also Python A valid variable name in , Usually used as a placeholder
for _ in range(5):
print(" Test caituotuo ")
for i in range(5):
print(" Test caituotuo ")
As can be seen from the above procedure , Use “_” Than using “i” Express more information , Is to tell others explicitly that this variable is useless .
_ Will point to the last expression you executed
Use a single underscore to format the value of a variable , For example, the amount , By this way we can make it easier to read
total_value = 8_000_000_000
print(total_value) # 8000000000
stay Python in , Prepositional underscores may affect variables in terms of semantics and functions .
_xxSingle underline in Python Medium name weak private （weak “internal use” ）, Semantically, it expresses private nature , That is to say, it is not an open interface , When you use from module import * It won't import Of variables that begin with a single underscore , But it can still be used if you force it , So it is called weak private .
class MyClass:
def _get_name(self):
print(" Test caituotuo ")
def get_name(self):
print(" Test caituotuo ")
__xxCorresponding to weak private is strong private , stay Python Of class definition It uses double pre underlined to indicate strong private , Forced quotation will result in an error , Can prevent being overridden by subclasses .
class MyClass:
def __get_name(self):
print(" Test caituotuo ")
In fact, strong private ownership can also be used , That is to say, a gentleman might as well be a villain ,Python It's actually in the class definition Rename the variables that begin with double underscores , Is to add a before the double downward stroke variable _class name , If the print is obj._MyClass__get_name(), It still works
xx_We know Python There are many key words in , for example ：class、def、return、pass……, They all have special definitions and meanings , So we can't use them to name variables or methods when defining them , For example, the following code is wrong ：
# Error model
def my_func(pass):
class = 1
return class
If that's how we want to define names , In order to distinguish between , You can add an underscore after （ However, it is not recommended to name it this way , Although it's legal , But there are so many names, why do you need to define keyword related names ）
def my_func(pass_):
class_ = 1
return class_
__xx__
dunderscore：double underscore
To express specifically Python Magic function in magic method, It's all some Python Some built-in functions , We can take it and use it , for example ： Class __init__、__call__ etc.
about Python For users, do not use , Never use this form in your own defined method （Never invent such names; only use them as documented.）
Do not cover when naming Python Methods built into （builtin method）
# Error model
list = [1, 2, 3, 4] # ×
dict = {"username": " Test caituotuo "} # ×
str = " Test caituotuo " # ×
When naming a file , And don't follow the built-in module The nuptial , for example ：os.py、selenium.py、turtle.py, It's not advisable .
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about Python I believe many pe
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