.NET/Java PDF, Tiff, Barcode SDK Library

Under each key, you store a list of people. In this case, the lists contain only me. Now, if you want a list of all the people registered who have the middle name Lie, you could do the following: >>> storage['middle']['Lie'] ['Magnus Lie Hetland'] As you can see, adding people to this structure is a bit tedious, especially when you get more people with the same first, middle, or last names, because then you have to extend the list that is already stored under that name. Let s add my sister, for example, and let s assume you don t know what is already stored in the database: >>> my_sister = 'Anne Lie Hetland' >>> storage['first'].setdefault('Anne', []).append(my_sister) >>> storage['middle'].setdefault('Lie', []).append(my_sister) >>> storage['last'].setdefault('Hetland', []).append(my_sister) >>> storage['first']['Anne'] ['Anne Lie Hetland'] >>> storage['middle']['Lie'] ['Magnus Lie Hetland', 'Anne Lie Hetland'] Imagine writing a large program filled with updates like this it would quickly become quite unwieldy. The point of abstraction is to hide all the gory details of the updates, and you can do that with functions. Let s first make a function to initialize a data structure: def init(data): data['first'] = {} data['middle'] = {} data['last'] = {} In the preceding code, I ve simply moved the initialization statements inside a function. You can use it like this:

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In this instance the file pointer was placed 8 bytes into the file before reading anything. This meant that Fred Blo was skipped, and only the rest of the line was retrieved.

Generic informational presentations normally lack a structure with a beginning, a middle, and an end, but with Act I as a structure, you know that you will start strong and end strong every time With Act II as.

The ability to jump easily around files, read lines based on delimiters, and handle data byte by byte makes Ruby ideal for manipulating data, but I haven t yet covered how to write new information to files or how to make changes to existing files. Generally, you can mirror most of the techniques used to read files when writing to files. For example:

This code creates a new file (or overwrites an existing file) called text.txt and puts a single line of text within it. Previously you ve used puts on its own to output data to the screen, but when used with a File object it writes the data to the file instead. Simple! The "w" passed as the second argument to File.open tells Ruby to open the file for writing only, and to create a new file or overwrite what is already in the file. This is in contrast with the "r" mode used earlier when opening a file for reading only. However, you can use several different file modes, as covered in Table 9-1.

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>>> storage = {} >>> init(storage) >>> storage {'middle': {}, 'last': {}, 'first': {}} As you can see, the function has taken care of the initialization, making the code much more readable.

Read-only. The file pointer is placed at the start of the file. Both reading and writing are allowed. The file pointer is placed at the start of the file. Write-only. A new file is created (or an old one overwritten as if new). Both reading and writing are allowed, but File.new creates a new file from scratch (or overwrites an old one as if new). Write (in append mode). The file pointer is placed at the end of the file and writes will make the file longer. Both reading and writing are allowed (in append mode). The file pointer is placed at the end of the file and writes will make the file longer. Binary file mode (only required on Windows). You can use it in conjunction with any of the other modes listed.

Using the append mode described in Table 9-1, it s trivial to create a program that appends a line of text to a file each time it s run: