Equal sign is the assignment operator
The equal sign is the main Python assignment operator aList 3.14e10, '2nd elmt of a list', 8.82-4.371j Be aware now that assignment does not explicitly assign a value to a variable, although it may appear that way from your experience with other programming languages. In Python, objects are referenced, so on assignment, a reference not a value to an object is what is being assigned, whether the object was just created or was a pre-existing object. If this is not 100 clear now, do not worry...
Triple Quotes
Although strings can be represented by single or double quote delimitation, it is often difficult to manipulate strings containing special or non-printable characters, especially the NEWLINE character. Python's triple quotes comes to the rescue by allowing strings to span multiple lines, including verbatim NEWLINEs, TABs, and any other special characters. The syntax for triple quotes consists of three consecutive single or double quotes used in pairs, naturally gt gt gt para_str this is a long...
What is ClientServer Architecture
What is client-server architecture It means different things to different people, depending on whom you ask as well as whether you are describing a software or a hardware system. In either case, the premise is simple The server, a piece of hardware or software, is providing a service which is needed by one or more clients, users of the service. Its sole purpose of existence is to wait for client requests, service those clients, then wait for more requests. Clients, on the other hand, contact a...
hasattr getattr setattr delattr
The attr functions can work with all kinds of objects, not just classes and instances. However, since they are most often used with those objects, we present them here. The hasattr obj, attr function is Boolean and its only function is to determine whether or not an object has a particular attribute, presumably used as a check before actually trying to access that attribute. The getattr and setattr functions retrieve and assign values to object attributes, respectively. getattr will raise an...
Standard Type Operators Adg
In Chapter 4, we introduced a number of operators that apply to most objects, including the standard types. We will take a look at how some of those apply to strings. For a brief introduction, here are a few examples using strings When using the value comparison operators, strings are compared lexicographically ASCII value order .
Builtin Functions BIFs
BIFs are generally written as extensions in C or C , compiled into the Python interpreter, and loaded into the system as part of the first built-in namespace. As mentioned in previous chapters, these functions are found in the_builtin_module and are imported into the interpreter as the _builtins_module. In restricted execution modes, only a subset of these functions is available. See Section 14.6 for more details on restricted execution. All BIFs come with the attributes given in Table 14.1....
try Dfd
8 Improvingraw_input . In the beginning of this chapter, we presented a safe version of the float built-in function to detect and handle two different types of exceptions which float generates. Likewise, the raw_input function can generate two different exceptions, either EOFError or KeyboardInterrupt on end-of-file EOF or cancelled input, respectively. Create a wrapper function, perhaps safe_input rather than raising an exception if the user entered EOF AD in Unix or AZ in DOS or attempted to...
Lines Tdr
We want to execute our test functions only when invoking this script directly, and that is what the code here does. Most of the scripts given in this text utilize the same format. Running this on a Unix machine, we get the following output ' usr tmp 18 908.1' FileError Errno 13 ' usr tmp 18 908.1' FileError Errno 13 ' usr tmp 18 908.1' FileError Errno 13 ' usr tmp 18 908.1' NetworkError Errno 146 Connection refused 'deli 8080 NetworkError Errno 6 host not found 'www 8080' The results are...
How to Do a Multuple Assignment
Another way of assigning multiple variables is using what we shall call the multuple assignment. This is not an official Python term, but we use multuple here because when assigning variables this way, the objects on both sides of the equals sign are tuples, a Python standard type we introduced in Section 2.8. gt gt gt x, y, z 1, 2, 'a string' gt gt gt x 1 In the above example, two integer objects with values 1 and 2 and one string object are assigned to x, y, and z respectively. Parentheses...