[Python-checkins] python/dist/src/Doc/whatsnew whatsnew24.tex, 1.45, 1.46 (original) (raw)

rhettinger at users.sourceforge.net rhettinger at users.sourceforge.net
Wed May 19 18:30:28 EDT 2004

Update of /cvsroot/python/python/dist/src/Doc/whatsnew In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv18496

Modified Files: whatsnew24.tex Log Message: Improved wording for generator expressions.

Index: whatsnew24.tex

RCS file: /cvsroot/python/python/dist/src/Doc/whatsnew/whatsnew24.tex,v retrieving revision 1.45 retrieving revision 1.46 diff -C2 -d -r1.45 -r1.46 *** whatsnew24.tex 19 May 2004 19:45:19 -0000 1.45 --- whatsnew24.tex 19 May 2004 22:30:25 -0000 1.46 *************** *** 15,20 **** \tableofcontents
! This article explains the new features in Python 2.4. No release date ! for Python 2.4 has been set; expect that this will happen mid-2004.
While Python 2.3 was primarily a library development release, Python --- 15,20 ---- \tableofcontents
! This article explains the new features in Python 2.4. The release ! date is expected to be around September 2004.
While Python 2.3 was primarily a library development release, Python *************** *** 92,101 **** \section{PEP 229: Generator Expressions}
! Generator expressions create in-line generators using a syntax similar ! to list comprehensions but with parenthesis instead of the surrounding ! brackets. ! ! Genexps allow simple generators to be constructed without a separate function ! definition. Writing:
\begin{verbatim} --- 92,101 ---- \section{PEP 229: Generator Expressions}
! Now, 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.
\begin{verbatim} *************** *** 122,130 **** more readily than with list comprehensions.
! Generator expressions are intended to be used inside functions ! such as \function{sum()}, \function{min()}, \function{set()}, and ! \function{dict()}. These functions consume their data all at once ! and would not benefit from having a full list instead of a generator ! as an input:
\begin{verbatim} --- 122,128 ---- more readily than with list comprehensions.
! Generator expressions are best used in functions that consume their ! data all at once and would not benefit from having a full list instead ! of a generator as an input:
\begin{verbatim} *************** *** 150,158 **** \end{verbatim}

- These examples show the intended use for generator expressions - in situations where the values get consumed immediately after the - generator is created. In these situations, they operate like - memory efficient versions of list comprehensions.

For more complex uses of generators, it is strongly recommended that the traditional full generator definitions be used instead. In a --- 148,151 ----

*** 160,167 **** as soon as the expression is defined while the other expressions do not get evaluated until the generator is run. This nuance is never ! an issue when the generator is used immediately. If it is not used ! right away, then it is better to write a full generator definition ! which more clearly reveals when the expressions are evaluated and is ! more obvious about the visibility and lifetime of its looping variables.

\begin{seealso} --- 153,160 ---- as soon as the expression is defined while the other expressions do not get evaluated until the generator is run. This nuance is never ! an issue when the generator is used immediately; however, if it is not ! used right away, a full generator definition would be much more clear ! about when the sub-expressions are evaluated and would be more obvious ! about the visibility and lifetime of the variables.

\begin{seealso}

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