Various ways to iterate over sequences The sequence functions illustrated in 4. We can randomize the contents of a list s before iterating over them, using random. We can convert between these sequence types. For example, tuple s converts any kind of sequence into a tuple, and list s converts any kind of sequence into a list.
You should see a result something like this: You might see other suffixes than those shown here. For example, if you have debugging enabled, you'll see a -debug suffix.
It's possible to set up the script so that it can be run by name without invoking Python explicitly. Under Unix, add an initial! This tells the system what program should execute the script. Many Unix accounts are set up not to search the current directory when looking for commands.
Instead, you can set up a filename association so that.
Instead of using chmod to make the script executable, open the Folder Options item in the Control Panel and select its File Types tab. File Types enables you to set up an association for files that end with.
Then you can invoke the script by name: For example, it doesn't catch exceptions or indicate what went wrong if an error occurs, and it doesn't allow for the possibility that the statement it runs might not return any results.
This section shows how to address these issues using a more elaborate script, animal. Error Handling After importing the requisite modules, animal. To allow for the possibility of connection failure for example, so that you can display the reason for the failureit's necessary to catch exceptions.
To handle exceptions in Python, put your code in a try statement and include an except clause that contains the error-handling code. The resulting connection sequence looks like this: Error in this example to obtain the database-specific error information that MySQLdb can provide, as well as a variable e in which to store the information.
If an exception occurs, MySQLdb makes this information available in e. The except clause shown in the example prints both values and exits.
The complete text of animal. Methods for Issuing Statements The next section of animal. Remember that it will be placed in a try statement; errors will trigger exceptions that are caught and handled in the corresponding except clause, which allows the main flow of the code to read more smoothly.
The statements perform the following actions: Drop the animal table if it already exists, to begin with a clean slate. Create the animal table.
Insert some data into the table and report the number of rows added. Each statement is issued by invoking the cursor object's execute method.
The first two statements produce no result, but the third produces a count indicating the number of rows inserted.
The count is available in the cursor's rowcount attribute. Some database interfaces provide this count as the return value of the statement-execution call, but that is not true for DB-API.
That is, execute only issues the statement, it does not return the result set. You can use fetchone to get the rows one at a time, or fetchall to get them all at once. Here's how to use fetchone for row-at-a-time retrieval: The loop checks for this and exits when the result set has been exhausted.
For each row returned, the tuple contains two values that's how many columns the SELECT statement asked forwhich animal. The print statement shown above accesses the individual tuple elements. However, because they are used in order of occurrence within the tuple, the print statement could just as well have been written like this: To access the individual row tuples, iterate through the row set that fetchall returns: Another way to determine the row count when you use fetchall is by taking the length of the value that it returns: It's also possible to fetch rows as dictionaries, which enables you to access column values by name.Because I telecommute, I'm limited to using my company's webmail interface, Microsoft Outlook Web Access, rather than having direct POP or IMAP access to e-mail.
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All Python program files will need to be saved with a “.py” extension. You can write the program in any text editor such as Notepad or Notepad++, just be sure to save the file with a “.py” extension.
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Topics concerned with writing providing Web applications, doing server-side programming, providing a Web site or pages which use Python in some way: WebFrameworks - for developing server-side Web applications in Python CgiScripts - information on writing CGI scripts/programs in Python when the.