Constants and variables are used to store data values in programming. A variable usually refers to a value that can change over time. A constant is a type of variable whose value cannot be changed during program execution.
There are only six built-in constants available in Python, they are False, True, None, Not Implemented, Ellipsis(...) and __debug__. Apart from these constants, Python does not have any built-in data types to store constant values.
Example
The following demonstrates an example of constants -
False = 100
Output
SyntaxError: cannot assign to False
False is a built-in constant in Python, used to store the Boolean value false. Assigning any value to it is illegal and will raise a SyntaxError.
But in the PEP 8 standard, constants are in uppercase. This helps the user know that it is a constant value. If we encounter any all-caps variables, by convention rather than rule, we should not change their values. Let's look at an example.
Example
π is a mathematical constant, approximately equal to 3.14159. Let us declare the value of the constant π in Python.
# declare constants PI = 3.14159 print(PI)
Output
3.14
In the example above, the mathematical constant pi is declared using all uppercase letters.
Example
As mentioned in the Constants section of PEP 8, we should use uppercase letters and underscores to separate words.
# declare constants LUMINOUS_EFFICACY = 683 VALUE_A = 100 COLOR = 'RED' print(LUMINOUS_EFFICACY) print(VALUE_A) print(COLOR)
Output
683 100 RED
As we can see, constants are also created exactly like variables. Both variables and constants follow similar naming rules, the only difference is that constants only use uppercase letters.
Example
Normally, in Python, constants are declared in modules. Let's take an example and create constants.
Declare constants in a separate file and name the file with a .py extension.
Constants.py file
# declare constants SPEED_OF_LIGHT_IN_VACUUM = 299792458 PI = 3.141592653589793 LUMINOUS_EFFICACY = 683 VALUE = 20
Example.py file
import Constants print(Constants.VALUE) print(Constants.SPEED_OF_LIGHT_IN_VACUUM) print(Constants.PI)
Output
20 299792458 3.141592653589793
In the above example, we created the Constants.py file, called the Constants module. Then, we declared some constant values. After that, we create another python file which is an Example.py file and in this file we import the Constant module using the import keyword. Finally, access the constant value.
The purpose of using uppercase letters is to indicate that the current name is considered a constant. But it doesn't actually prevent the reallocation of constant values.
The above is the detailed content of How to create a constant in Python?. For more information, please follow other related articles on the PHP Chinese website!

The reasons why Python scripts cannot run on Unix systems include: 1) Insufficient permissions, using chmod xyour_script.py to grant execution permissions; 2) Shebang line is incorrect or missing, you should use #!/usr/bin/envpython; 3) The environment variables are not set properly, and you can print os.environ debugging; 4) Using the wrong Python version, you can specify the version on the Shebang line or the command line; 5) Dependency problems, using virtual environment to isolate dependencies; 6) Syntax errors, using python-mpy_compileyour_script.py to detect.

Using Python arrays is more suitable for processing large amounts of numerical data than lists. 1) Arrays save more memory, 2) Arrays are faster to operate by numerical values, 3) Arrays force type consistency, 4) Arrays are compatible with C arrays, but are not as flexible and convenient as lists.

Listsare Better ForeflexibilityandMixdatatatypes, Whilearraysares Superior Sumerical Computation Sand Larged Datasets.1) Unselable List Xibility, MixedDatatypes, andfrequent elementchanges.2) Usarray's sensory -sensical operations, Largedatasets, AndwhenMemoryEfficiency

NumPymanagesmemoryforlargearraysefficientlyusingviews,copies,andmemory-mappedfiles.1)Viewsallowslicingwithoutcopying,directlymodifyingtheoriginalarray.2)Copiescanbecreatedwiththecopy()methodforpreservingdata.3)Memory-mappedfileshandlemassivedatasetsb

ListsinPythondonotrequireimportingamodule,whilearraysfromthearraymoduledoneedanimport.1)Listsarebuilt-in,versatile,andcanholdmixeddatatypes.2)Arraysaremorememory-efficientfornumericdatabutlessflexible,requiringallelementstobeofthesametype.

Pythonlistscanstoreanydatatype,arraymodulearraysstoreonetype,andNumPyarraysarefornumericalcomputations.1)Listsareversatilebutlessmemory-efficient.2)Arraymodulearraysarememory-efficientforhomogeneousdata.3)NumPyarraysareoptimizedforperformanceinscient

WhenyouattempttostoreavalueofthewrongdatatypeinaPythonarray,you'llencounteraTypeError.Thisisduetothearraymodule'sstricttypeenforcement,whichrequiresallelementstobeofthesametypeasspecifiedbythetypecode.Forperformancereasons,arraysaremoreefficientthanl

Pythonlistsarepartofthestandardlibrary,whilearraysarenot.Listsarebuilt-in,versatile,andusedforstoringcollections,whereasarraysareprovidedbythearraymoduleandlesscommonlyusedduetolimitedfunctionality.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

SublimeText3 English version
Recommended: Win version, supports code prompts!

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

SublimeText3 Chinese version
Chinese version, very easy to use

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function
