\subsection{Numeric Types \label{typesnumeric}}
-There are four numeric types: \dfn{plain integers}, \dfn{long integers},
+There are four numeric types: \dfn{plain integers}, \dfn{long integers},
\dfn{floating point numbers}, and \dfn{complex numbers}.
Plain integers (also just called \dfn{integers})
are implemented using \ctype{long} in C, which gives them at least 32
Complex numbers have a real and imaginary part, which are both
implemented using \ctype{double} in C. To extract these parts from
-a complex number \var{z}, use \code{\var{z}.real} and \code{\var{z}.imag}.
+a complex number \var{z}, use \code{\var{z}.real} and \code{\var{z}.imag}.
Numbers are created by numeric literals or as the result of built-in
functions and operators. Unadorned integer literals (including hex
\item[(1)]
For (plain or long) integer division, the result is an integer.
-The result is always rounded towards minus infinity: 1/2 is 0,
+The result is always rounded towards minus infinity: 1/2 is 0,
(-1)/2 is -1, 1/(-2) is -1, and (-1)/(-2) is 0. Note that the result
is a long integer if either operand is a long integer, regardless of
the numeric value.
the end of the string: \code{len(\var{s}) + \var{i}} or
\code{len(\var{s}) + \var{j}} is substituted. But note that \code{-0} is
still \code{0}.
-
+
\item[(3)] The slice of \var{s} from \var{i} to \var{j} is defined as
the sequence of items with index \var{k} such that \code{\var{i} <=
\var{k} < \var{j}}. If \var{i} or \var{j} is greater than
Additional string operations are defined in standard modules
\refmodule{string}\refstmodindex{string} and
-\refmodule{re}.\refstmodindex{re}
+\refmodule{re}.\refstmodindex{re}
\subsubsection{XRange Type \label{typesseq-xrange}}
no longer works in Python 2.0. Use of this misfeature has been
deprecated since Python 1.4.
-\item[(2)] Raises an exception when \var{x} is not a list object. The
+\item[(2)] Raises an exception when \var{x} is not a list object. The
\method{extend()} method is experimental and not supported by
mutable sequence types other than lists.
File objects\obindex{file} are implemented using C's \code{stdio}
package and can be created with the built-in constructor
-\function{file()}\bifuncindex{file} described in section
+\function{file()}\bifuncindex{file} described in section
\ref{built-in-funcs}, ``Built-in Functions.''\footnote{\function{file()}
is new in Python 2.2. The older built-in \function{open()} is an
alias for \function{file()}.}
\begin{methoddesc}[file]{readline}{\optional{size}}
Read one entire line from the file. A trailing newline character is
kept in the string\footnote{
- The advantage of leaving the newline on is that an empty string
- can be returned to mean \EOF{} without being ambiguous. Another
- advantage is that (in cases where it might matter, for example. if you
- want to make an exact copy of a file while scanning its lines)
+ The advantage of leaving the newline on is that an empty string
+ can be returned to mean \EOF{} without being ambiguous. Another
+ advantage is that (in cases where it might matter, for example. if you
+ want to make an exact copy of a file while scanning its lines)
you can tell whether the last line of a file ended in a newline
or not (yes this happens!).
} (but may be absent when a file ends with an
\end{methoddesc}
\begin{methoddesc}[file]{truncate}{\optional{size}}
- Truncate the file's size. If the optional \var{size} argument is
+ Truncate the file's size. If the optional \var{size} argument
present, the file is truncated to (at most) that size. The size
- defaults to the current position. The current file position is
- not changed. Note that if a specified size exceeds the file's
- current size, the result is platform-dependent: possibilities
- include that file may remain unchanged, increase to the specified
- size as if zero-filled, or increase to the specified size with
- undefined new content.
- Availability: Windows, many \UNIX variants.
+ defaults to the current position. Availability of this function
+ depends on the operating system version (for example, not all
+ \UNIX{} versions support this operation).
\end{methoddesc}
\begin{methoddesc}[file]{write}{str}
expect(f.read(1), 'a') # the 'a' that was written at the end of the file above
f.close()
-if hasattr(f, 'truncate'):
- if test_support.verbose:
- print 'try truncate'
- f = open(name, 'r+b')
- f.seek(0, 2)
- expect(f.tell(), size+1) # else we've lost track of the true size
- # Cut it back via seek + truncate with no argument.
- newsize = size - 10
- f.seek(newsize)
- f.truncate()
- expect(f.tell(), newsize) # else pointer moved
- f.seek(0, 2)
- expect(f.tell(), newsize) # else wasn't truncated
- # Ensure that truncate(smaller than true size) shrinks the file.
- newsize -= 1
- f.seek(42)
- f.truncate(newsize)
- expect(f.tell(), 42) # else pointer moved
- f.seek(0, 2)
- expect(f.tell(), newsize) # else wasn't truncated
-
- # XXX truncate(larger than true size) is ill-defined across platforms
-
- # cut it waaaaay back
- f.seek(0)
- f.truncate(1)
- expect(f.tell(), 0) # else pointer moved
- expect(len(f.read()), 1) # else wasn't truncated
-
- f.close()
+
+# XXX add tests for truncate if it exists
+# XXX has truncate ever worked on Windows? specifically on WinNT I get:
+# "IOError: [Errno 13] Permission denied"
+##try:
+## newsize = size - 10
+## f.seek(newsize)
+## f.truncate()
+## expect(f.tell(), newsize)
+## newsize = newsize - 1
+## f.seek(0)
+## f.truncate(newsize)
+## expect(f.tell(), newsize)
+##except AttributeError:
+## pass
os.unlink(name)
#ifdef MS_WIN32
#define fileno _fileno
-/* can simulate truncate with Win32 API functions; see file_truncate */
+/* can (almost fully) duplicate with _chsize, see file_truncate */
#define HAVE_FTRUNCATE
-#define WINDOWS_LEAN_AND_MEAN
-#include <windows.h>
#endif
#ifdef macintosh
newsizeobj = NULL;
if (!PyArg_ParseTuple(args, "|O:truncate", &newsizeobj))
return NULL;
-
- /* Set newsize to current postion if newsizeobj NULL, else to the
- specified value. */
if (newsizeobj != NULL) {
#if !defined(HAVE_LARGEFILE_SUPPORT)
newsize = PyInt_AsLong(newsizeobj);
#endif
if (PyErr_Occurred())
return NULL;
- }
- else {
- /* Default to current position. */
+ } else {
+ /* Default to current position*/
Py_BEGIN_ALLOW_THREADS
errno = 0;
newsize = _portable_ftell(f->f_fp);
Py_END_ALLOW_THREADS
- if (newsize == -1)
- goto onioerror;
+ if (newsize == -1) {
+ PyErr_SetFromErrno(PyExc_IOError);
+ clearerr(f->f_fp);
+ return NULL;
+ }
}
-
- /* Flush the file. */
Py_BEGIN_ALLOW_THREADS
errno = 0;
ret = fflush(f->f_fp);
Py_END_ALLOW_THREADS
- if (ret != 0)
- goto onioerror;
+ if (ret != 0) goto onioerror;
#ifdef MS_WIN32
- /* MS _chsize doesn't work if newsize doesn't fit in 32 bits,
- so don't even try using it. */
- {
- Py_off_t current; /* current file position */
- HANDLE hFile;
- int error;
-
- /* current <- current file postion. */
- if (newsizeobj == NULL)
- current = newsize;
- else {
- Py_BEGIN_ALLOW_THREADS
- errno = 0;
- current = _portable_ftell(f->f_fp);
- Py_END_ALLOW_THREADS
- if (current == -1)
- goto onioerror;
- }
-
- /* Move to newsize. */
- if (current != newsize) {
- Py_BEGIN_ALLOW_THREADS
- errno = 0;
- error = _portable_fseek(f->f_fp, newsize, SEEK_SET)
- != 0;
- Py_END_ALLOW_THREADS
- if (error)
- goto onioerror;
- }
-
- /* Truncate. Note that this may grow the file! */
+ /* can use _chsize; if, however, the newsize overflows 32-bits then
+ _chsize is *not* adequate; in this case, an OverflowError is raised */
+ if (newsize > LONG_MAX) {
+ PyErr_SetString(PyExc_OverflowError,
+ "the new size is too long for _chsize (it is limited to 32-bit values)");
+ return NULL;
+ } else {
Py_BEGIN_ALLOW_THREADS
errno = 0;
- hFile = (HANDLE)_get_osfhandle(fileno(f->f_fp));
- error = hFile == (HANDLE)-1;
- if (!error) {
- error = SetEndOfFile(hFile) == 0;
- if (error)
- errno = EACCES;
- }
+ ret = _chsize(fileno(f->f_fp), (long)newsize);
Py_END_ALLOW_THREADS
- if (error)
- goto onioerror;
-
- /* Restore original file position. */
- if (current != newsize) {
- Py_BEGIN_ALLOW_THREADS
- errno = 0;
- error = _portable_fseek(f->f_fp, current, SEEK_SET)
- != 0;
- Py_END_ALLOW_THREADS
- if (error)
- goto onioerror;
- }
+ if (ret != 0) goto onioerror;
}
#else
Py_BEGIN_ALLOW_THREADS
projects / thirdparty / Python / cpython.git / commitdiff
