Introduction to Parsing in Java

Paint GTIN - 12 in Java Introduction to Parsing
14 Introduction to Parsing
Encode UPC A In Java
Using Barcode encoder for Java Control to generate, create UPC Symbol image in Java applications.
object We convert this object into a standard Python list, so now we have a list containing a single item a list of our results which we assign to the items variable, and that we then further process via the populate_children() call Before discussing the handling of the results, we will brie y mention the error handling If the parser fails it will raise an exception We don t want PyParsing s exceptions to leak out to clients since we may choose to change the parser generator later on So, if an exception occurs, we catch it and then raise our own exception (a ValueError) with the relevant details
Bar Code Creation In Java
Using Barcode generation for Java Control to generate, create barcode image in Java applications.
hierarchyblk
Scan Bar Code In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
le 525
Encode GTIN - 12 In Visual Studio .NET
Using Barcode creator for ASP.NET Control to generate, create UPC-A Supplement 2 image in ASP.NET applications.
In the case of a successful parse of the hierarchyblk example, the items list looks like this (with occurrences of <BlockBlock object at 0x8f52acd> and similar, replaced with Block for clarity):
Encoding UCC - 12 In .NET
Using Barcode generation for .NET framework Control to generate, create UPC Code image in VS .NET applications.
[0, Block, [], 2, 0, Block, [], 2, Block, [], 0, Block, []]
Data Matrix Creation In Java
Using Barcode creation for Java Control to generate, create Data Matrix image in Java applications.
Whenever we parsed an empty block we returned 0 to the parser s results list; whenever we parsed new rows we returned the number of rows; and whenever we encountered a node_data, we created a Block to represent it In the case of Blocks they always have an empty child list (ie, the children attribute is set to []), since at this point we don t know if the block will have children or not So here the outer list represents the root block, the 0s represent empty blocks, the other integers (all 2s in this case) represent new rows, and the []s are empty child lists since none of the hierarchyblk le s blocks contain other blocks
Generating Barcode In Java
Using Barcode generation for Java Control to generate, create bar code image in Java applications.
messageboxblk
EAN / UCC - 13 Encoder In Java
Using Barcode encoder for Java Control to generate, create EAN128 image in Java applications.
The messageboxblk example s items list (pretty printed to reveal its structure, and again using Block for clarity) is:
Bar Code Generator In Java
Using Barcode encoder for Java Control to generate, create bar code image in Java applications.
[Block, [Block, [0, Block, [], 2, Block, [], 0, Block, [], 1, 0] ] ]
Create GTIN - 12 In Java
Using Barcode maker for Java Control to generate, create Universal Product Code version A image in Java applications.
le 526
Paint I-2/5 In Java
Using Barcode drawer for Java Control to generate, create 2 of 5 Interleaved image in Java applications.
Here we can see that the outer list (representing the root block) contains a block that has a child list of one block that contains its own child list, and where these children are blocks (with their own empty child lists), new rows (2 and 1), and empty blocks (0s) One problem with the list results representation is that every Block s children list is empty each block s children are in a list that follows the block in the parser s results list We need to convert this structure into a single root block with child blocks To this end we have created a stack a list containing a single root Block We then call the populate_children() function that takes the list of items returned by the parser and a list with a root block, and populates the root block s children (and their children, and so on, as appropriate) with the items
Encode USS Code 39 In VB.NET
Using Barcode drawer for .NET framework Control to generate, create Code 39 Full ASCII image in .NET framework applications.
Pythonic Parsing with PyParsing The populate_children() function is quite short, but also rather subtle
Making Code 39 In Visual Studio .NET
Using Barcode drawer for Visual Studio .NET Control to generate, create Code 39 image in .NET framework applications.
def populate_children(items, stack): for item in items: if isinstance(item, BlockBlock): stack[-1]childrenappend(item) elif isinstance(item, list) and item: stackappend(stack[-1]children[-1]) populate_children(item, stack) stackpop() elif isinstance(item, int): if item == EmptyBlock: stack[-1]childrenappend(Blockget_empty_block()) else: for x in range(item): stack[-1]childrenappend(Blockget_new_row())
Data Matrix ECC200 Creator In C#
Using Barcode maker for Visual Studio .NET Control to generate, create Data Matrix ECC200 image in .NET applications.
We iterate over every item in the results list If the item is a Block we append it to the stack s last (top) Block s child list (Recall that the stack is initialized with a single root Block item) If the item is a nonempty list, then it is a child list that belongs to the previous block So we append the previous block (ie, the top Block s last child) to the stack to make it the top of the stack, and then recursively call populate_children() on the list item and the stack This ensures that the list item (ie, its child items) is appended to the correct item s child list Once the recursive call is nished, we pop the top of the stack, ready for the next item If the item is an integer then it is either an empty block (0, ie, EmptyBlock) or a count of new rows If it is an empty block we append an empty block to the stack s top Block s list of children If the item is a new row count, we append that number of new rows to the stack s top Block s list of children If the item is an empty list this signi es an empty child list and we do nothing, since by default all Blocks are initialized to have an empty child list At the end the stack s top item is still the root Block, but now it has children (which may have their own children, and so on) For the hierarchyblk example, the populate_children() function produces the structure illustrated in Figure 1413 (528 ) And for the messageboxblk example, the function produces the structure illustrated in Figure 1414 (528 ) The conversion into an SVG le using the BlockOutputsave_blocks_as_svg() function is the same for all the blocks parsers, since they all produce the same root block and children structures
Read Barcode In VS .NET
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in .NET applications.
Barcode Printer In C#.NET
Using Barcode creator for VS .NET Control to generate, create bar code image in VS .NET applications.
Draw DataMatrix In Visual Studio .NET
Using Barcode creator for ASP.NET Control to generate, create Data Matrix image in ASP.NET applications.
Bar Code Printer In Visual C#
Using Barcode maker for Visual Studio .NET Control to generate, create bar code image in .NET framework applications.