Folder iterator

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Resumes a file iteration using a continuation token from a previous iterator. continue Folder Iterator(continuationToken) Folder Iterator: Resumes a folder iteration using a Iterators. Now we can start to use V8 iterators, by converting a Drive files or folders iterator into proper V8 iterators. Get a v8 iterator from a files or folders iterator. Although these examples

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sngz/Folder-Iterator: Solution to folder iterator problem - GitHub

GO!riterate("YOUR/FOLDER/");Well… You guys should be masters of recursive functions by now.EXTRA) COMBINING GLOB & ITERATOR5-glob-iterate.php// (A) GLOB ITERATOR$dir = "D:/DOCS/";$eol = PHP_EOL;// $iterator = new ArrayObject(glob("$dir*.{jpg,jpeg,gif,png,bmp,webp}", GLOB_BRACE));$iterator = new ArrayObject(glob("$dir*", GLOB_BRACE));$iterator = $iterator->getIterator(); /* (B) OPTIONAL - PAGINATION$pgNow = 0; // current page$pgPage = 10; // entries per page$iterator = new LimitIterator($iterator, $pgNow * $pgPer, $pgPer);*/ // (C) LOOPforeach ($iterator as $ff) { if (is_file($ff)) { echo "{$ff} - file {$eol}"; } if (is_dir($ff)) { echo "{$ff} - folder {$eol}"; }}Which is the “best method”? I will say “all of them”, whichever works for you is the best. But personally, my “best solution” is a combination of glob and iterator – This is very flexible, capable of restricting by the file types, and also easily do pagination with it.LINKS & REFERENCESScandir – PHPReaddir – PHPGlob – PHPDirectory Iterator – PHPGet Files By Extensions, Prefix, Suffix, Date – Code BoxxTHE ENDThank you for reading, and we have come to the end. I hope that it has helped you to better understand, and if you want to share anything with this guide, please feel free to comment below. Good luck and happy coding!

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folder-iterator/folder-iterator.ps1 at master mhtvsSFrpHdE/folder

Class FileIterator Stay organized with collections Save and categorize content based on your preferences. An iterator that allows scripts to iterate over a potentially large collection of files. Fileiterators can be accessed from DriveApp or a Folder.// Log the name of every file in the user's Drive.const files = DriveApp.getFiles();while (files.hasNext()) { const file = files.next(); Logger.log(file.getName());}MethodsMethodReturn typeBrief descriptiongetContinuationToken()StringGets a token that can be used to resume this iteration at a later time.hasNext()BooleanDetermines whether calling next() will return an item.next()FileGets the next item in the collection of files or folders.Detailed documentationgetContinuationToken()Gets a token that can be used to resume this iteration at a later time. This method is usefulif processing an iterator in one execution would exceed the maximum execution time.Continuation tokens are generally valid for one week.ReturnString — a continuation token that can be used to resume this iteration with the items that remained in the iterator when the token was generatedhasNext()Determines whether calling next() will return an item.ReturnBoolean — true if next() will return an item; false if notnext()Gets the next item in the collection of files or folders. Throws an exception if no itemsremain.ReturnFile — the next item in the collection Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates. Last updated 2024-12-02 UTC.

Iterating through files in a folder with nested folders - Cocoa

Template class M >std::pairiterator, bool> insert_or_assign( const key_type& k, M&& obj ); (1) (since C++23) template class M >std::pairiterator, bool> insert_or_assign( key_type&& k, M&& obj ); (2) (since C++23) template class K, class M >std::pairiterator, bool> insert_or_assign( K&& k, M&& obj ); (3)(since C++23) template class M >iterator insert_or_assign( const_iterator hint, const key_type& k, M&& obj ); (4) (since C++23) template class M >iterator insert_or_assign( const_iterator hint, key_type&& k, M&& obj ); (5) (since C++23) template class K, class M >iterator insert_or_assign( const_iterator hint, K&& k, M&& obj ); (6)(since C++23) The conversion from k into key_type must construct an object u, for which find(k) == find(u) is true. Otherwise, the behavior is undefined.[edit] Parameters k - the key used both to look up and to insert if not found hint - iterator to the position before which the new element will be inserted obj - the value to insert or assign[edit] Return value1-3) The bool component is true if the insertion took place and false if the assignment took place. The iterator component is pointing at the element that was inserted or updated.4-6) Iterator pointing at the element that was inserted or updated.[edit] Complexity[edit] Notesinsert_or_assign returns more information than operator[] and does not require default-constructibility of the mapped type.[edit] Example#include #include #include void print_node(const auto& node){ std::cout '[' node.first "] = " node.second '\n';} void print_result(auto const& pair){ std::cout (pair.second ? "inserted: " : "assigned: "); print_node(*pair.first);} int main(){ std::flat_mapstd::string, std::string> map; print_result(map.insert_or_assign("a", "apple")); print_result(map.insert_or_assign("b", "banana")); print_result(map.insert_or_assign("c", "cherry")); print_result(map.insert_or_assign("c",. Resumes a file iteration using a continuation token from a previous iterator. continue Folder Iterator(continuationToken) Folder Iterator: Resumes a folder iteration using a Iterators. Now we can start to use V8 iterators, by converting a Drive files or folders iterator into proper V8 iterators. Get a v8 iterator from a files or folders iterator. Although these examples

Microsoft Graph SDK: Iterate folders and sub-folders

Iterator of batches instead of a single input batch as input.Returns an iterator of output batches instead of a single output batch.The length of the entire output in the iterator should be the same as the length of the entire input.The wrapped pandas UDF takes a single Spark column as an input.You should specify the Python type hint asIterator[pandas.Series] -> Iterator[pandas.Series].This pandas UDF is useful when the UDF execution requires initializing some state, for example,loading a machine learning model file to apply inference to every input batch.The following example shows how to create a pandas UDF with iterator support.Pythonimport pandas as pdfrom typing import Iteratorfrom pyspark.sql.functions import col, pandas_udf, structpdf = pd.DataFrame([1, 2, 3], columns=["x"])df = spark.createDataFrame(pdf)# When the UDF is called with the column,# the input to the underlying function is an iterator of pd.Series.@pandas_udf("long")def plus_one(batch_iter: Iterator[pd.Series]) -> Iterator[pd.Series]: for x in batch_iter: yield x + 1df.select(plus_one(col("x"))).show()# +-----------+# |plus_one(x)|# +-----------+# | 2|# | 3|# | 4|# +-----------+# In the UDF, you can initialize some state before processing batches.# Wrap your code with try/finally or use context managers to ensure# the release of resources at the end.y_bc = spark.sparkContext.broadcast(1)@pandas_udf("long")def plus_y(batch_iter: Iterator[pd.Series]) -> Iterator[pd.Series]: y = y_bc.value # initialize states try: for x in batch_iter: yield x + y finally: pass # release resources here, if anydf.select(plus_y(col("x"))).show()# +---------+# |plus_y(x)|# +---------+# | 2|# | 3|# | 4|# +---------+Iterator of multiple Series to Iterator of Series UDF​An Iterator of multiple Series to Iterator of Series UDF has similar characteristics andrestrictions as Iterator of Series to Iterator of Series UDF. The specified function takes an iterator of batches andoutputs an iterator of batches. It is also useful when the UDF execution requires initializing somestate.The differences are:The underlying Python function takes an iterator of a tuple of pandas Series.The wrapped pandas UDF takes multiple Spark

Google Drive File Iterator within Folder iterator - Stack Overflow

Presentation on theme: "Interator and Iterable"— Presentation transcript: 1 Interator and IterableTwo commonly used interfaces in Java. And: for-each loop. >"> 2 >Iterator Problem: how can we access all members of a collection without knowing the structure of the collection? Solution: each collection (List, Set, Stack, ...) provides an Iterator we can use. > Iterator hasNext( ): boolean next( ): T (Object) remove(): void list ="> 3 How to Use Iterator List list =new ArrayList( ); list.add("apple"); list.add( ); // add stuff Iterator iter = list.iterator(); while ( iter.hasNext() ) { String s = iter.next( ); // do something with s } create a new Iterator for the collection. 4 Iterator Reduces DependencySuppose we have a Purse that contains Coins and a method getContents to show what is in the purse: // Suppose a purse has a collection of coins List coins = purse.getContents(); for(int k=0; k Coin c = coins.get(k); //TODO process this coin } Now the Purse must always create a List for us, even if the coins are stored is some other kind of collection, or a database. 5 Iterator Reduces Dependency (2)If getContents instead just returns an Iterator, then: // Suppose a purse has a collection of coins Iterator coins = purse.getContents(); while( coins.hasNext() ) { Coin c = coins.next(); //TODO process this coin } The purse is free to internally use any collection it wants, and does not need to create a List for us. >"> 6 >Iterable Problem: how can we get an Iterator? Forces: (1) the collection should create the iterator itself since only the collection knows its own elements. (2) every collection should provide same interface for getting an Iterator (for polymorphism). Solution: define an interface for creating iterators. Make each collection implement this interface. > Iterable iterator( ): Iterator list ="> 7 How to Use Iterable List list =new ArrayList( ); list.add( ... ); Iterator iter = list.iterator(); iterator() creates a new Iterator each time. 8 Iterable is a Factory MethodYou can eliminate direct dependency between classes by creating an interface for required behavior. the factory... the product... abstract: the factory method concrete: 9 Factory Method The Pattern Factory Interface Iterable Factory Methoditerator( ) Product Iterator Concrete Factory any collection list ="> 10 for-each loop List list =new ArrayList( ); list.add( ); // add things to list // print the list for( String s: list ) { System.out.println(s); } "for each

Lua folder iterator example GitHub

Columns as an input.You specify the type hints as Iterator[Tuple[pandas.Series, ...]] -> Iterator[pandas.Series].Pythonfrom typing import Iterator, Tupleimport pandas as pdfrom pyspark.sql.functions import col, pandas_udf, structpdf = pd.DataFrame([1, 2, 3], columns=["x"])df = spark.createDataFrame(pdf)@pandas_udf("long")def multiply_two_cols( iterator: Iterator[Tuple[pd.Series, pd.Series]]) -> Iterator[pd.Series]: for a, b in iterator: yield a * bdf.select(multiply_two_cols("x", "x")).show()# +-----------------------+# |multiply_two_cols(x, x)|# +-----------------------+# | 1|# | 4|# | 9|# +-----------------------+Series to scalar UDF​Series to scalar pandas UDFs are similar to Spark aggregate functions.A Series to scalar pandas UDF defines an aggregation from one or morepandas Series to a scalar value, where each pandas Series represents a Spark column.You use a Series to scalar pandas UDF with APIs such as select, withColumn, groupBy.agg, andpyspark.sql.Window.You express the type hint as pandas.Series, ... -> Any. The return type should be aprimitive data type, and the returned scalar can be either a Python primitive type, for example,int or float or a NumPy data type such as numpy.int64 or numpy.float64. Any should ideallybe a specific scalar type.This type of UDF does not support partial aggregation and all data for each group is loaded into memory.The following example shows how to use this type of UDF to compute mean with select, groupBy, and window operations:Pythonimport pandas as pdfrom pyspark.sql.functions import pandas_udffrom pyspark.sql import Windowdf = spark.createDataFrame( [(1, 1.0), (1, 2.0), (2, 3.0), (2, 5.0), (2, 10.0)], ("id", "v"))# Declare the function and create the UDF@pandas_udf("double")def mean_udf(v: pd.Series) -> float: return v.mean()df.select(mean_udf(df['v'])).show()# +-----------+# |mean_udf(v)|# +-----------+# | 4.2|# +-----------+df.groupby("id").agg(mean_udf(df['v'])).show()# +---+-----------+# | id|mean_udf(v)|# +---+-----------+# | 1| 1.5|# | 2| 6.0|# +---+-----------+w = Window \ .partitionBy('id') \ .rowsBetween(Window.unboundedPreceding, Window.unboundedFollowing)df.withColumn('mean_v', mean_udf(df['v']).over(w)).show()# +---+----+------+# | id| v|mean_v|# +---+----+------+# | 1| 1.0| 1.5|# | 1| 2.0| 1.5|# | 2| 3.0| 6.0|# | 2| 5.0| 6.0|# | 2|10.0| 6.0|# +---+----+------+For detailed usage, see pyspark.sql.functions.pandas_udf.Usage​Setting Arrow batch size​noteThis configuration has no impact on compute configured with standard

GAS Google Folder/File Iterator

ListReturns:true if this list changed as a result of the callThrows:ClassCastException - if the class of an element of this list is incompatible with the specified collection (optional)NullPointerException - if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is nullSee Also:Collection.contains(Object)retainAllpublic boolean retainAll​(Collection c)Retains only the elements in this list that are contained in the specified collection. In other words, removes from this list all of its elements that are not contained in the specified collection.Specified by:retainAll in interface CollectionE>Specified by:retainAll in interface ListE>Overrides:retainAll in class AbstractCollectionE>Parameters:c - collection containing elements to be retained in this listReturns:true if this list changed as a result of the callThrows:ClassCastException - if the class of an element of this list is incompatible with the specified collection (optional)NullPointerException - if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is nullSee Also:Collection.contains(Object)listIteratorReturns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list. The specified index indicates the first element that would be returned by an initial call to next. An initial call to previous would return the element with the specified index minus one. The returned list iterator is fail-fast.Specified by:listIterator in interface ListE>Overrides:listIterator in class AbstractListE>Parameters:index - index of the first element to be returned from the list iterator (by a call to next)Returns:a list iterator over the elements in this list (in proper sequence), starting at the specified position in the listThrows:IndexOutOfBoundsException - if the index is out of range (index size())listIteratorReturns a list iterator over the elements in this list (in proper sequence). The returned list iterator is fail-fast.Specified by:listIterator in interface ListE>Overrides:listIterator in class AbstractListE>Returns:a list iterator over the elements in this list (in proper sequence)See Also:listIterator(int)iteratorReturns an iterator over the elements in this list in proper sequence. The returned iterator is fail-fast.Specified by:iterator in interface CollectionE>Specified by:iterator in interface IterableE>Specified by:iterator in interface ListE>Overrides:iterator in class AbstractListE>Returns:an iterator over the elements in this list. Resumes a file iteration using a continuation token from a previous iterator. continue Folder Iterator(continuationToken) Folder Iterator: Resumes a folder iteration using a

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folder-iterator/README.md at master - GitHub

Start, VM Stop actions. Feature - Azure Storage - Added Storage File Copy Show, Storage File Copy Start, Storage File Copy Stop, Storage File Delete, Storage File Download, Storage File List, Storage File Upload actions. Enhancement - VS.NET Action - Error message for missing .Net framework now reports the required .Net framework name. Enhancement - Delphi Build - Now reports the location of cfg file when created, or where it was to be located if creation fails. Enhancement - Delphi Build - Added protection for blank directory values when variables used. Bug Fix - FTPS Actions - Corrected divide by zero error for upload progress. Bug Fix - FTPS Actions - Corrected potential duplication of folder delimiters depending on server type. Bug Fix - Export Log Action - Corrected issue where exporting a log in an included project export everything currently in the log, including the parent project. Bug Fix - Delphi Build Action - Fixed loading of D10Seattle VCL Styles, deal with upgraded dproj files being incorrect. Bug Fix - CSV Iterator Action - Corrected csv iterator to correctly determine if the last field was quoted or not. Bug Fix - COM+ Action - Corrected issue where COM+ errors would not be reported correctly. FinalBuilder Core Feature - Added FBPROJECTEXT variable. It contains the file extension of the loaded FinalBuilder project. E.g. ".fbp" Bug Fix - Added better encoding detection for text files that do not have a byte order mark. Bug Fix - Corrected an error in loading FinalBuilder 4 projects into FinalBuilder 8. Bug Fix - Corrected an error in loading FinalBuilder 7 projects into FinalBuilder 8 that caused variables to be reported as no longer defined. FinalBuilder 8.0.0.1520 February 3rd, 2016 FinalBuilder IDE Bug Fix - Corrected logging of async group child actions. Multiple runs of

Iterating Through Files in a Folder. Example

String s in list" { } 11 for-each compared to whileFor-each loop. stuff is any Collection or an array. for( Object x: stuff) { System.out.println( x ); } While loop does same thing: Iterator iterator = stuff.iterator( ); while( iterator.hasNext() ) { Object x = iterator.next( ); System.out.println( x ); } 12 for-each in detail "For each Datatype x in ... do { . . . }"for( Datatype x: _collection_ ) { System.out.println(x); } Datatype of the elements in _collection_ _collection_ can be: 1) array 2) any Iterable object 13 for-each with array Indexed for loop. array[ ] is an array of doubledouble [] array = . . .; for(int k=0; k System.out.println(array[k]); } for-each loop to do the same thing: for( double x: array ) { System.out.println( x ); } 14 Error: modifying a collection while using iteratorIterator throws an exception if the underlying collection is modified while using the iterator. List words = /* a list of strings */; Iterator iter = words.iterator( ); System.out.println(iter.next()); // OK words.add("elephant"); System.out.println(iter.next()); // error // exception thrown "for-each" also throws exception if you modify collection while inside loop. (what about for-each with array?). Resumes a file iteration using a continuation token from a previous iterator. continue Folder Iterator(continuationToken) Folder Iterator: Resumes a folder iteration using a Iterators. Now we can start to use V8 iterators, by converting a Drive files or folders iterator into proper V8 iterators. Get a v8 iterator from a files or folders iterator. Although these examples

Iterate through S3 folder and compare images inside that folder?

Command has been processed asynchronously to inform therender process of whether some or all of the data updates have not beenapplied in the queueDataUpdates function.Render::RenderBase::applyPendingDataUpdates: Called ifhasPendingDataUpdates returns true. This is used to facilitate a workflowwhere a set of updates are queued in the update thread and then flushed in themain thread.Render::RenderBase::processControlCommand: Calledwhen a custom live render command is executed.Render::RenderBase::stopLiveEditing: Called when a liverender is stopped by the user.Processing the Katana recipe and utility classes¶Interpreting the Katana recipe into the renderer’s language involves a deferredevaluation of the scene graph. This is done by traversing the scene graph usinga FnScenegraphIterator starting from theroot. The render plug-in can get the root iterator usingRender::RenderBase::getRootIterator.Each iterator corresponds to a scene graph location which contains a set ofcorresponding attributes.Scene graph location types and attributes are based on conventions where therender plug-in can selectively handle location types and attributes that areapplicable to the renderer.Scene graph delegates¶The handling of scene graph locations and their attributes can be dynamicallydelegated to Render::ScenegraphLocationDelegate plug-ins.Given an arbitrary scene graph iterator (e.g. FnScenegraphIterator sgi), we can check if a corresponding delegateplug-in exists and invoke it using RenderOutputUtils::processLocationbool pluginFound = RenderOutputUtils::processLocation(sgi, "myrenderer", sgi.getType(), 0x0, 0x0);Scene graph utility classes¶Utility classes are provided to parse standardised attribute conventions wherethey can be extended to provide renderer-specific behaviour through overrides:Render::RenderSettings: ParsesrenderSettings at /root.Render::CameraSettings: Parsescamera.geometry at /root/world/cam/[cameraName].Render::GlobalSettings: Parses[rendererName]GlobalStatements at /root (seeConfiguring global settings).RenderOutputUtils: A collection of useful utility functions.Tip:Avoid using the iterator function getByPath to get an iterator for alocation that has already been traversed as it will

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User7011

GO!riterate("YOUR/FOLDER/");Well… You guys should be masters of recursive functions by now.EXTRA) COMBINING GLOB & ITERATOR5-glob-iterate.php// (A) GLOB ITERATOR$dir = "D:/DOCS/";$eol = PHP_EOL;// $iterator = new ArrayObject(glob("$dir*.{jpg,jpeg,gif,png,bmp,webp}", GLOB_BRACE));$iterator = new ArrayObject(glob("$dir*", GLOB_BRACE));$iterator = $iterator->getIterator(); /* (B) OPTIONAL - PAGINATION$pgNow = 0; // current page$pgPage = 10; // entries per page$iterator = new LimitIterator($iterator, $pgNow * $pgPer, $pgPer);*/ // (C) LOOPforeach ($iterator as $ff) { if (is_file($ff)) { echo "{$ff} - file {$eol}"; } if (is_dir($ff)) { echo "{$ff} - folder {$eol}"; }}Which is the “best method”? I will say “all of them”, whichever works for you is the best. But personally, my “best solution” is a combination of glob and iterator – This is very flexible, capable of restricting by the file types, and also easily do pagination with it.LINKS & REFERENCESScandir – PHPReaddir – PHPGlob – PHPDirectory Iterator – PHPGet Files By Extensions, Prefix, Suffix, Date – Code BoxxTHE ENDThank you for reading, and we have come to the end. I hope that it has helped you to better understand, and if you want to share anything with this guide, please feel free to comment below. Good luck and happy coding!

2025-04-10
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Class FileIterator Stay organized with collections Save and categorize content based on your preferences. An iterator that allows scripts to iterate over a potentially large collection of files. Fileiterators can be accessed from DriveApp or a Folder.// Log the name of every file in the user's Drive.const files = DriveApp.getFiles();while (files.hasNext()) { const file = files.next(); Logger.log(file.getName());}MethodsMethodReturn typeBrief descriptiongetContinuationToken()StringGets a token that can be used to resume this iteration at a later time.hasNext()BooleanDetermines whether calling next() will return an item.next()FileGets the next item in the collection of files or folders.Detailed documentationgetContinuationToken()Gets a token that can be used to resume this iteration at a later time. This method is usefulif processing an iterator in one execution would exceed the maximum execution time.Continuation tokens are generally valid for one week.ReturnString — a continuation token that can be used to resume this iteration with the items that remained in the iterator when the token was generatedhasNext()Determines whether calling next() will return an item.ReturnBoolean — true if next() will return an item; false if notnext()Gets the next item in the collection of files or folders. Throws an exception if no itemsremain.ReturnFile — the next item in the collection Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates. Last updated 2024-12-02 UTC.

2025-04-22
User6932

Iterator of batches instead of a single input batch as input.Returns an iterator of output batches instead of a single output batch.The length of the entire output in the iterator should be the same as the length of the entire input.The wrapped pandas UDF takes a single Spark column as an input.You should specify the Python type hint asIterator[pandas.Series] -> Iterator[pandas.Series].This pandas UDF is useful when the UDF execution requires initializing some state, for example,loading a machine learning model file to apply inference to every input batch.The following example shows how to create a pandas UDF with iterator support.Pythonimport pandas as pdfrom typing import Iteratorfrom pyspark.sql.functions import col, pandas_udf, structpdf = pd.DataFrame([1, 2, 3], columns=["x"])df = spark.createDataFrame(pdf)# When the UDF is called with the column,# the input to the underlying function is an iterator of pd.Series.@pandas_udf("long")def plus_one(batch_iter: Iterator[pd.Series]) -> Iterator[pd.Series]: for x in batch_iter: yield x + 1df.select(plus_one(col("x"))).show()# +-----------+# |plus_one(x)|# +-----------+# | 2|# | 3|# | 4|# +-----------+# In the UDF, you can initialize some state before processing batches.# Wrap your code with try/finally or use context managers to ensure# the release of resources at the end.y_bc = spark.sparkContext.broadcast(1)@pandas_udf("long")def plus_y(batch_iter: Iterator[pd.Series]) -> Iterator[pd.Series]: y = y_bc.value # initialize states try: for x in batch_iter: yield x + y finally: pass # release resources here, if anydf.select(plus_y(col("x"))).show()# +---------+# |plus_y(x)|# +---------+# | 2|# | 3|# | 4|# +---------+Iterator of multiple Series to Iterator of Series UDF​An Iterator of multiple Series to Iterator of Series UDF has similar characteristics andrestrictions as Iterator of Series to Iterator of Series UDF. The specified function takes an iterator of batches andoutputs an iterator of batches. It is also useful when the UDF execution requires initializing somestate.The differences are:The underlying Python function takes an iterator of a tuple of pandas Series.The wrapped pandas UDF takes multiple Spark

2025-03-28
User5449

Presentation on theme: "Interator and Iterable"— Presentation transcript: 1 Interator and IterableTwo commonly used interfaces in Java. And: for-each loop. >"> 2 >Iterator Problem: how can we access all members of a collection without knowing the structure of the collection? Solution: each collection (List, Set, Stack, ...) provides an Iterator we can use. > Iterator hasNext( ): boolean next( ): T (Object) remove(): void list ="> 3 How to Use Iterator List list =new ArrayList( ); list.add("apple"); list.add( ); // add stuff Iterator iter = list.iterator(); while ( iter.hasNext() ) { String s = iter.next( ); // do something with s } create a new Iterator for the collection. 4 Iterator Reduces DependencySuppose we have a Purse that contains Coins and a method getContents to show what is in the purse: // Suppose a purse has a collection of coins List coins = purse.getContents(); for(int k=0; k Coin c = coins.get(k); //TODO process this coin } Now the Purse must always create a List for us, even if the coins are stored is some other kind of collection, or a database. 5 Iterator Reduces Dependency (2)If getContents instead just returns an Iterator, then: // Suppose a purse has a collection of coins Iterator coins = purse.getContents(); while( coins.hasNext() ) { Coin c = coins.next(); //TODO process this coin } The purse is free to internally use any collection it wants, and does not need to create a List for us. >"> 6 >Iterable Problem: how can we get an Iterator? Forces: (1) the collection should create the iterator itself since only the collection knows its own elements. (2) every collection should provide same interface for getting an Iterator (for polymorphism). Solution: define an interface for creating iterators. Make each collection implement this interface. > Iterable iterator( ): Iterator list ="> 7 How to Use Iterable List list =new ArrayList( ); list.add( ... ); Iterator iter = list.iterator(); iterator() creates a new Iterator each time. 8 Iterable is a Factory MethodYou can eliminate direct dependency between classes by creating an interface for required behavior. the factory... the product... abstract: the factory method concrete: 9 Factory Method The Pattern Factory Interface Iterable Factory Methoditerator( ) Product Iterator Concrete Factory any collection list ="> 10 for-each loop List list =new ArrayList( ); list.add( ); // add things to list // print the list for( String s: list ) { System.out.println(s); } "for each

2025-04-06
User8956

ListReturns:true if this list changed as a result of the callThrows:ClassCastException - if the class of an element of this list is incompatible with the specified collection (optional)NullPointerException - if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is nullSee Also:Collection.contains(Object)retainAllpublic boolean retainAll​(Collection c)Retains only the elements in this list that are contained in the specified collection. In other words, removes from this list all of its elements that are not contained in the specified collection.Specified by:retainAll in interface CollectionE>Specified by:retainAll in interface ListE>Overrides:retainAll in class AbstractCollectionE>Parameters:c - collection containing elements to be retained in this listReturns:true if this list changed as a result of the callThrows:ClassCastException - if the class of an element of this list is incompatible with the specified collection (optional)NullPointerException - if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is nullSee Also:Collection.contains(Object)listIteratorReturns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list. The specified index indicates the first element that would be returned by an initial call to next. An initial call to previous would return the element with the specified index minus one. The returned list iterator is fail-fast.Specified by:listIterator in interface ListE>Overrides:listIterator in class AbstractListE>Parameters:index - index of the first element to be returned from the list iterator (by a call to next)Returns:a list iterator over the elements in this list (in proper sequence), starting at the specified position in the listThrows:IndexOutOfBoundsException - if the index is out of range (index size())listIteratorReturns a list iterator over the elements in this list (in proper sequence). The returned list iterator is fail-fast.Specified by:listIterator in interface ListE>Overrides:listIterator in class AbstractListE>Returns:a list iterator over the elements in this list (in proper sequence)See Also:listIterator(int)iteratorReturns an iterator over the elements in this list in proper sequence. The returned iterator is fail-fast.Specified by:iterator in interface CollectionE>Specified by:iterator in interface IterableE>Specified by:iterator in interface ListE>Overrides:iterator in class AbstractListE>Returns:an iterator over the elements in this list

2025-04-07

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