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Close bug 480337: Dict used before dicts explained. Added explanation

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and examples of the dict() constructor.
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Raymond Hettinger 2002-06-25 15:13:18 +00:00
parent 04e7e0c60f
commit 07dc91800f
1 changed files with 11 additions and 2 deletions
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13
Doc/tut/tut.tex
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@ -1843,8 +1843,6 @@ parenthesized.
[12, 18]
>>> [3*x for x in vec if x < 2]
[]
>>> [{x: x**2} for x in vec]
[{2: 4}, {4: 16}, {6: 36}]
>>> [[x,x**2] for x in vec]
[[2, 4], [4, 16], [6, 36]]
>>> [x, x**2 for x in vec] # error - parens required for tuples
@ -2023,6 +2021,17 @@ Here is a small example using a dictionary:
1
\end{verbatim}
The \function{dict()} contructor builds dictionaries directly from
lists of key-value pairs stored as tuples. When the pairs form a
pattern, list comprehensions can compactly specify the key-value list.
\begin{verbatim}
>>> dict([('sape', 4139), ('guido', 4127), ('jack', 4098)])
{'sape': 4139, 'jack': 4098, 'guido': 4127}
>>> dict([(x, x**2) for x in vec]) # use a list comprehension
{2: 4, 4: 16, 6: 36}
\end{verbatim}
\section{Looping Techniques \label{loopidioms}}