- Python Cookbook
- Foreword
- Preface
- 1. Python Shortcuts
- Introduction
- Swapping Values WithoutUsing a Temporary Variable
- Constructing a Dictionary Without Excessive Quoting
- Getting a Value from a Dictionary
- Adding an Entry to a Dictionary
- Associating Multiple Values with Each Key in a Dictionary
- Dispatching Using a Dictionary
- Collecting a Bunch of Named Items
- Finding the Intersection of Two Dictionaries
- Assigning and Testing with One Statement
- Using List Comprehensions Instead of map and filter
- Unzipping Simple List-Like Objects
- Flattening a Nested Sequence
- Looping in Parallel over Index and Sequence Items
- Looping Through Multiple Lists
- Spanning a Range Defined by Floats
- Transposing Two-Dimensional Arrays
- Creating Lists of Lists Without Sharing References
- 2. Searching and Sorting
- Introduction
- Sorting a Dictionary
- Processing Selected Pairs of Structured Data Efficiently
- Sorting While Guaranteeing Sort Stability
- Sorting by One Field, Then by Another
- Looking for Items in a Sorted Sequence Using Binary Search
- Sorting a List of Objects by an Attribute of the Objects
- Sorting by Item or by Attribute
- Selecting Random Elements from a List Without Repetition
- Performing Frequent Membership Tests on a Sequence
- Finding the Deep Index of an Item in an Embedded Sequence
- Showing Off Quicksort in Three Lines
- Sorting Objects Using SQL’s ORDER BY Syntax
- 3. Text
- Introduction
- Processing a String One Character at a Time
- Testing if an Object Is String-Like
- Aligning Strings
- Trimming Space from the Ends of a String
- Combining Strings
- Checking Whether a String Contains a Set of Characters
- Filtering a String for a Set of Characters
- Controlling Case
- Reversing a String by Words or Characters
- Accessing Substrings
- Changing the Indentation of a Multiline String
- Testing Whether a String Represents an Integer
- Expanding and Compressing Tabs
- Replacing Multiple Patterns in a Single Pass
- Converting Between Different Naming Conventions
- Converting Between Characters and Values
- Converting Between Unicode and Plain Strings
- Printing Unicode Characters to Standard Output
- Dispatching Based on Pattern Matches
- Evaluating Code Inside Strings
- Replacing Python Code with the Results of Executing That Code
- Module: Yet Another Python Templating Utility (YAPTU)
- Module: Roman Numerals
- 4. Files
- Introduction
- Reading from a File
- Writing to a File
- Searching and Replacing Text in a File
- Reading a Particular Line from a File
- Retrieving a Line at Random from a File of Unknown Size
- Counting Lines in a File
- Processing Every Word in a File
- Reading a Text File by Paragraphs
- Reading Lines with Continuation Characters
- Reading Data from ZIP Files
- Reading INI Configuration Files
- Sending Binary Data to Standard Output Under Windows
- Using Random-Access Input/Output
- Updating a Random-Access File
- Splitting a Path into All of Its Parts
- Treating Pathnames as Objects
- Creating Directories Including Necessary Parent Directories
- Walking Directory Trees
- Swapping One File Extension for Another Throughout a Directory Tree
- Finding a File Given an Arbitrary Search Path
- Finding a File on the Python Search Path
- Dynamically Changing the Python Search Path
- Computing Directory Sizes in a Cross-Platform Way
- File Locking Using a Cross-Platform API
- Versioning Filenames
- Module: Versioned Backups
- 5. Object-Oriented Programming
- Introduction
- Overriding a Built-In Method
- Getting All Members of a Class Hierarchy
- Calling a Superclass _ _init_ _ Method if It Exists
- Calling a Superclass Implementation of a Method
- Implementing Properties
- Implementing Static Methods
- Implementing Class Methods
- Delegating Automatically as an Alternative to Inheritance
- Decorating an Object with Print-Like Methods
- Checking if an Object Has Necessary Attributes
- Making a Fast Copy of an Object
- Adding Methods to a Class at Runtime
- Modifying the Class Hierarchy of an Instance
- Keeping References to Bound Methods Without Inhibiting Garbage Collection
- Defining Constants
- Managing Options
- Implementing a Set Class
- Implementing a Ring Buffer
- Implementing a Collection
- Delegating Messages to Multiple Objects
- Implementing the Singleton Design Pattern
- Avoiding the Singleton Design Pattern with the Borg Idiom
- Implementing the Null Object Design Pattern
- 6. Threads, Processes, and Synchronization
- Introduction
- Storing Per-Thread Information
- Terminating a Thread
- Allowing Multithreaded Read Access While Maintaining a Write Lock
- Running Functions in the Future
- Synchronizing All Methods in an Object
- Capturing the Output and Error Streams from a Unix Shell Command
- Forking a Daemon Process on Unix
- Determining if Another Instance of a Script Is Already Running in Windows
- Processing Windows Messages Using MsgWaitForMultipleObjects
- 7. System Administration
- Introduction
- Running a Command Repeatedly
- Generating Random Passwords
- Generating Non-Totally Random Passwords
- Checking the Status of a Unix Network Interface
- Calculating Apache Hits per IP Address
- Calculating the Rate of Client Cache Hits on Apache
- Manipulating the Environment on Windows NT/2000/XP
- Checking and Modifying the Set of Tasks Windows Automatically Runs at Logon
- Examining the Microsoft Windows Registry for a List of Name Server Addresses
- Getting Information About the Current User on Windows NT/2000
- Getting the Windows Service Name from Its Long Name
- Manipulating Windows Services
- Impersonating Principals on Windows
- Changing a Windows NT Password Using ADSI
- Working with Windows Scripting Host (WSH) from Python
- Displaying Decoded Hotkeys for Shortcuts in Windows
- 8. Databases and Persistence
- Introduction
- Serializing Data Using the marshal Module
- Serializing Data Using the pickle and cPickle Modules
- Using the cPickle Module on Classes and Instances
- Mutating Objects with shelve
- Accessing a MySQL Database
- Storing a BLOB in a MySQL Database
- Storing a BLOB in a PostgreSQL Database
- Generating a Dictionary Mapping from Field Names to Column Numbers
- Using dtuple for Flexible Access to Query Results
- Pretty-Printing the Contents of Database Cursors
- Establishing Database Connections Lazily
- Accessing a JDBC Database from a Jython Servlet
- Module: jet2sql—Creating a SQL DDL from an Access Database
- 9. User Interfaces
- Introduction
- Avoiding lambda in Writing Callback Functions
- Creating Menus with Tkinter
- Creating Dialog Boxes with Tkinter
- Supporting Multiple Values per Row in a Tkinter Listbox
- Embedding Inline GIFs Using Tkinter
- Combining Tkinter and Asynchronous I/O with Threads
- Using a wxPython Notebook with Panels
- Giving the User Unobtrusive Feedback During Data Entry with Qt
- Building GUI Solutions Independent of the Specific GUI Toolkit
- Creating Color Scales
- Using Publish/Subscribe Broadcasting to Loosen the Coupling Between GUI and Business Logic Systems
- Module: Building GTK GUIs Interactively
- 10. Network Programming
- Introduction
- Writing a TCP Client
- Writing a TCP Server
- Passing Messages with Socket Datagrams
- Finding Your Own Name and Address
- Converting IP Addresses
- Grabbing a Document from the Web
- Being an FTP Client
- Sending HTML Mail
- Sending Multipart MIME Email
- Bundling Files in a MIME Message
- Unpacking a Multipart MIME Message
- Module: PyHeartBeat—Detecting Inactive Computers
- Module: Interactive POP3 Mailbox Inspector
- Module: Watching for New IMAP Mail Using a GUI
- 11. Web Programming
- Introduction
- Testing Whether CGI Is Working
- Writing a CGI Script
- Using a Simple Dictionary for CGI Parameters
- Handling URLs Within a CGI Script
- Resuming the HTTP Download of a File
- Stripping Dangerous Tags and Javascript from HTML
- Running a Servlet with Jython
- Accessing Netscape Cookie Information
- Finding an Internet Explorer Cookie
- Module: Fetching Latitude/Longitude Data from the Web
- 12. Processing XML
- Introduction
- Checking XML Well-Formedness
- Counting Tags in a Document
- Extracting Text from an XML Document
- Transforming an XML Document Using XSLT
- Transforming an XML Document Using Python
- Parsing an XML File with xml.parsers.expat
- Converting Ad-Hoc Text into XML Markup
- Normalizing an XML Document
- Controlling XSLT Stylesheet Loading
- Autodetecting XML Encoding
- Module: XML Lexing (Shallow Parsing)
- Module: Converting a List of Equal-Length Lists into XML
- 13. Distributed Programming
- Introduction
- Making an XML-RPC Method Call
- Serving XML-RPC Requests
- Using XML-RPC with Medusa
- Writing a Web Service That Supports Both XML-RPC and SOAP
- Implementing a CORBA Client and Server
- Performing Remote Logins Using telnetlib
- Using Publish/Subscribe in a Distributed Middleware Architecture
- Using Request/Reply in a Distributed Middleware Architecture
- 14. Debugging and Testing
- Introduction
- Reloading All Loaded Modules
- Tracing Expressions and Comments in Debug Mode
- Wrapping Tracebacks in HTML
- Getting More Information from Tracebacks
- Starting the Debugger Automatically After an Uncaught Exception
- Logging and Tracing Across Platforms
- Determining the Name of the Current Function
- Introspecting the Call Stack with Older Versions of Python
- Debugging the Garbage-Collection Process
- Tracking Instances of Particular Classes
- 15. Programs About Programs
- Introduction
- Colorizing Python Source Using the Built-in Tokenizer
- Importing a Dynamically Generated Module
- Importing from a Module Whose Name Is Determined at Runtime
- Importing Modules with Automatic End-of-Line Conversions
- Simulating Enumerations in Python
- Modifying Methods in Place
- Associating Parameters with a Function (Currying)
- Composing Functions
- Adding Functionality to a Class
- Adding a Method to a Class Instance at Runtime
- Defining a Custom Metaclass to Control Class Behavior
- Module: Allowing the Python Profiler to Profile C Modules
- 16. Extending and Embedding
- Introduction
- Implementing a Simple Extension Type
- Translating a Python Sequence into a C Array with the PySequence_Fast Protocol
- Accessing a Python Sequence Item-by-Item with the Iterator Protocol
- Returning None from a Python-Callable C Function
- Coding the Methods of a Python Class in C
- Implementing C Function Callbacks to a Python Function
- Debugging Dynamically Loaded C Extensions with gdb
- Debugging Memory Problems
- Using SWIG-Generated Modules in a Multithreaded Environment
- 17. Algorithms
- Introduction
- Testing if a Variable Is Defined
- Evaluating Predicate Tests Across Sequences
- Removing Duplicates from a Sequence
- Removing Duplicates from a Sequence While Maintaining Sequence Order
- Simulating the Ternary Operator in Python
- Counting Items and Sorting by Incidence (Histograms)
- Memoizing (Caching) the Return Values of Functions
- Looking Up Words by Sound Similarity
- Computing Factorials with lambda
- Generating the Fibonacci Sequence
- Wrapping an Unbounded Iterator to Restrict Its Output
- Operating on Iterators
- Rolling Dice
- Implementing a First-In First-Out Container
- Modeling a Priority Queue
- Converting Numbers to Rationals via Farey Fractions
- Evaluating a Polynomial
- Module: Finding the Convex Hull of a Set of 2D Points
- Module: Parsing a String into a Date/Time Object Portably
- 18. List of Contributors
- Index
- Colophon
Credit: Luther Blissett
That’s what the
ljust,
rjust, and
center methods of string objects are for. Each
takes a single argument, the width of the string you want as a
result, and returns the starting string with spaces on either or both
sides:
>>> print '|', 'hej'.ljust(20), '|', 'hej'.rjust(20), '|', 'hej'.center(20), '|'
| hej | hej | hej |'.Centering, left-justifying, or right-justifying text comes up surprisingly often—for example, when you want to print a simple report with centered page numbers. Because of this, Python string objects supply this functionality through their methods.
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