Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "We created a shapefile Reader object instance and set it to the variable r".

A block of code is set as follows:

>>> import math
>>> x1 = 456456.23123582301
>>> y1 = 1279721.064356426
>>> x2 = 576628.34295886324
>>> y2 = 1071740.3328161312
>>> x_dist = x1 - x2
>>> y_dist = y1 - y2
>>> dist_sq = x_dist**2 + y_dist**2
>>> distance = math.sqrt(dist_sq)
>>> distance
240202.6667795573

Any command-line input or output is written as follows:

C:\>python
Python 2.7.2 (default, Jun 12 2011, 15:08:59) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes, for example, appear in the text like this: "In the Properties window, select the Advanced tab".

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.