pseudo-code as an intermediate step before the implementation of designprogrammers are often asked to describe algorithms in way that is intended for human eyes only such descriptions are called pseudo-code pseudo-code is not computer programbut is more structured than usual prose it is mixture of natural language and high-level programming constructs that describe the main ideas behind generic implementation of data structure or algorithm because pseudo-code is designed for human readernot computerwe can communicate high-level ideaswithout being burdened with low-level implementation details at the same timewe should not gloss over important steps like many forms of human communicationfinding the right balance is an important skill that is refined through practice in this bookwe rely on pseudo-code style that we hope will be evident to python programmersyet with mix of mathematical notations and english prose for examplewe might use the phrase "indicate an errorrather than formal raise statement following conventions of pythonwe rely on indentation to indicate the extent of control structures and on an indexing notation in which entries of sequence with length are indexed from [ to [ howeverwe choose to enclose comments within curly braces like these in our pseudo-coderather than using python' character coding style and documentation programs should be made easy to read and understand good programmers should therefore be mindful of their coding styleand develop style that communicates the important aspects of program' design for both humans and computers conventions for coding style tend to vary between different programming communities the official style guide for python code is available online at the main principles that we adopt are as followspython code blocks are typically indented by spaces howeverto avoid having our code fragments overrun the book' marginswe use spaces for each level of indentation it is strongly recommended that tabs be avoidedas tabs are displayed with differing widths across systemsand tabs and spaces are not viewed as identical by the python interpreter many python-aware editors will automatically replace tabs with an appropriate number of spaces