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Diffstat (limited to 'Doc/ref6.tex')
| -rw-r--r-- | Doc/ref6.tex | 36 |
1 files changed, 22 insertions, 14 deletions
diff --git a/Doc/ref6.tex b/Doc/ref6.tex index afd9822..0baaf05 100644 --- a/Doc/ref6.tex +++ b/Doc/ref6.tex @@ -30,24 +30,24 @@ returns no meaningful result; in Python, procedures return the value \verb@None@): \begin{verbatim} -expression_stmt: expression_list +expression_stmt: condition_list \end{verbatim} -An expression statement evaluates the expression list (which may be a -single expression). If the value is not \verb@None@, it is converted +An expression statement evaluates the condition list (which may be a +single condition). +\indexii{expression}{list} + +In interactive mode, if the value is not \verb@None@, it is converted to a string using the rules for string conversions (expressions in reverse quotes), and the resulting string is written to standard output (see section \ref{print}) on a line by itself. -\indexii{expression}{list} +(The exception for \verb@None@ is made so that procedure calls, which +are syntactically equivalent to expressions, do not cause any output.) \ttindex{None} \indexii{string}{conversion} \index{output} \indexii{standard}{output} \indexii{writing}{values} - -(The exception for \verb@None@ is made so that procedure calls, which -are syntactically equivalent to expressions, do not cause any output. -A tuple with only \verb@None@ items is written normally.) \indexii{procedure}{call} \section{Assignment statements} @@ -224,7 +224,7 @@ required syntactically, but no code needs to be executed, for example: \begin{verbatim} def f(arg): pass # a function that does nothing (yet) -class C: pass # an class with no methods (yet) +class C: pass # a class with no methods (yet) \end{verbatim} \section{The {\tt del} statement} @@ -320,7 +320,7 @@ before really leaving the function. \stindex{raise} \begin{verbatim} -raise_stmt: "raise" condition ["," condition] +raise_stmt: "raise" condition ["," condition ["," condition]] \end{verbatim} \verb@raise@ evaluates its first condition, which must yield @@ -337,7 +337,15 @@ If the first object is a class or string, it then raises the exception identified by the first object, with the second one (or \verb@None@) as its parameter. If the first object is an instance, it raises the exception identified by the class of the object, with the instance as -its parameter. +its parameter (and there should be no second object, or the second +object should be \verb@None@). + +If a third object is present, and it it not \verb@None@, it should be +a traceback object (see section \ref{traceback}), and it is +substituted instead of the current location as the place where the +exception occurred. This is useful to re-raise an exception +transparently in an except clause. +\obindex{traceback} \section{The {\tt break} statement} \stindex{break} @@ -525,6 +533,6 @@ must be dictionaries and they are used for the global and local variables, respectively. Hints: dynamic evaluation of expressions is supported by the built-in -function \verb@eval()@. The built-in function \verb@vars()@ returns -the current local dictionary, which may be useful to pass around for -use by \verb@exec@. +function \verb@eval()@. The built-in functions \verb@globals()@ and +\verb@locals()@ return the current global and local dictionary, +respectively, which may be useful to pass around for use by \verb@exec@. |