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-rw-r--r-- | Doc/tut/tut.tex | 33 |
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diff --git a/Doc/tut/tut.tex b/Doc/tut/tut.tex index 87bc424..c8c5afe 100644 --- a/Doc/tut/tut.tex +++ b/Doc/tut/tut.tex @@ -4399,6 +4399,39 @@ generators terminate, they automatically raise \exception{StopIteration}. In combination, these features make it easy to create iterators with no more effort than writing a regular function. +\section{Generator Expressions\label{genexps}} + +Some simple generators can be coded succinctly as expressions using a syntax +like list comprehensions but with parentheses instead of brackets. These +expressions are designed for situations where the generator is used right +away by an enclosing function. Generator expressions are more compact but +less versatile than full generator definitions and the tend to be more memory +friendly than equivalent list comprehensions. + +Examples: + +\begin{verbatim} +>>> sum(i*i for i in range(10)) # sum of squares +285 + +>>> xvec = [10, 20, 30] +>>> yvec = [7, 5, 3] +>>> sum(x*y for x,y in zip(xvec, yvec)) # dot product +260 + +>>> from math import pi, sin +>>> sine_table = dict((x, sin(x*pi/180)) for x in range(0, 91)) + +>>> unique_words = set(word for line in page for word in line.split()) + +>>> valedictorian = max((student.gpa, student.name) for student in graduates) + +>>> data = 'golf' +>>> list(data[i] for i in range(len(data)-1,-1,-1)) +['f', 'l', 'o', 'g'] + +\end{verbatim} + \chapter{Brief Tour of the Standard Library \label{briefTour}} |