Python global and nonlocal

Compare global and nonlocal variables. These keywords change how variables are referenced in methods.

Global, nonlocal. Variable names are sometimes conflicting. In a method, an identifier may reference a local variable or a global variable. The global and nonlocal keywords indicate which variable is being referenced.

This program uses the global keyword. In method(), we use the statement "global value." This means that the identifier "value" refers to the global "value," which is accessed outside the method.

Result: The variable is changed to equal 100 in method(). And this is reflected in the global variable at the end of the program.

Python program that uses global def method(): # Change "value" to mean the global variable. # ... The assignment will be local without "global." global value value = 100 value = 0 method() # The value has been changed to 100. print(value) Output 100

Nonlocal. Nonlocal is similar in meaning to global. But it takes effect primarily in nested methods. It means "not a global or local variable." So it changes the identifier to refer to an enclosing method's variable.

Here: Method2() uses nonlocal to reference the "value" variable from method(). It will never reference a local or a global.

Python program that uses nonlocal def method(): def method2(): # In nested method, reference nonlocal variable. nonlocal value value = 100 # Set local. value = 10 method2() # Local variable reflects nonlocal change. print(value) # Call method. method() Output 100

Discussion. I was interested in why these keywords were needed. They tend to make Python programs more complex and, in my opinion, ugly. Nonlocal was added to make functions nest better—so they are more easily moved or pasted.

Without nonlocal: There was no way to avoid naming conflicts between locals and enclosing methods. Global was not sufficient.

Quote: But in Python, though functions are usually defined at the top level, a function definition can be executed anywhere. This... yielded inconsistencies that were surprising to some programmers.

PEP 3104 Access to Names in Outer Scopes: python.org

Summary. Global and nonlocal are not needed in many (probably most) Python programs. But, when needed, they make methods conflict less with enclosing methods or the global scope. They make the syntax, however, more complex.Built-ins

The Dev Codes

.Net

.NET Array Dictionary List String 2D Async DataTable Dates DateTime Enum File For Foreach Format IEnumerable If IndexOf Lambda LINQ Parse Path Process Property Regex Replace Sort Split Static StringBuilder Substring Switch Tuple

Java

Core Array ArrayList HashMap String 2D Cast Character Console Deque Duplicates File For Format HashSet If IndexOf Lambda Math ParseInt Process Random Regex Replace Sort Split StringBuilder Substring Switch Vector While

Related Links

Adjectives Ado Ai Android Angular Antonyms Apache Articles Asp Autocad Automata Aws Azure Basic Binary Bitcoin Blockchain C Cassandra Change Coa Computer Control Cpp Create Creating C-Sharp Cyber Daa Data Dbms Deletion Devops Difference Discrete Es6 Ethical Examples Features Firebase Flutter Fs Git Go Hbase History Hive Hiveql How Html Idioms Insertion Installing Ios Java Joomla Js Kafka Kali Laravel Logical Machine Matlab Matrix Mongodb Mysql One Opencv Oracle Ordering Os Pandas Php Pig Pl Postgresql Powershell Prepositions Program Python React Ruby Scala Selecting Selenium Sentence Seo Sharepoint Software Spellings Spotting Spring Sql Sqlite Sqoop Svn Swift Synonyms Talend Testng Types Uml Unity Vbnet Verbal Webdriver What Wpf

TheDeveloperBlog.com

Python global and nonlocal

Related Links:

.Net

Java

Related Links