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| 1 | +% Documentation heavily adapted from module docstring. |
| 2 | + |
| 3 | +\section{Standard Module \module{fileinput}} |
| 4 | +\stmodindex{fileinput} |
| 5 | +\label{module-fileinput} |
| 6 | + |
| 7 | +This module implements a helper class and functions to quickly write a |
| 8 | +loop over standard input or a list of files. |
| 9 | + |
| 10 | +The typical use is: |
| 11 | + |
| 12 | +\begin{verbatim} |
| 13 | +import fileinput |
| 14 | +for line in fileinput.input(): |
| 15 | + process(line) |
| 16 | +\end{verbatim} |
| 17 | + |
| 18 | +This iterates over the lines of all files listed in |
| 19 | +\code{sys.argv[1:]}, defaulting to \code{sys.stdin} if the list is |
| 20 | +empty. If a filename is \code{'-'}, it is also replaced by |
| 21 | +\code{sys.stdin}. To specify an alternative list of filenames, pass |
| 22 | +it as the first argument to \function{input()}. A single file name is |
| 23 | +also allowed. |
| 24 | + |
| 25 | +All files are opened in text mode. If an I/O error occurs during |
| 26 | +opening or reading a file, \exception{IOError} is raised. |
| 27 | + |
| 28 | +If \code{sys.stdin} is used more than once, the second and further use |
| 29 | +will return no lines, except perhaps for interactive use, or if it has |
| 30 | +been explicitly reset (e.g. using \code{sys.stdin.seek(0)}). |
| 31 | + |
| 32 | +Empty files are opened and immediately closed; the only time their |
| 33 | +presence in the list of filenames is noticeable at all is when the |
| 34 | +last file opened is empty. |
| 35 | + |
| 36 | +It is possible that the last line of a file does not end in a newline |
| 37 | +character; lines are returned including the trailing newline when it |
| 38 | +is present. |
| 39 | + |
| 40 | +The following function is the primary interface of this module: |
| 41 | + |
| 42 | +\begin{funcdesc}{input}{\optional{files\optional{, |
| 43 | + inplace\optional{, backup}}}} |
| 44 | + Create an instance of the \class{FileInput} class. The instance |
| 45 | + will be used as global state for the functions of this module, and |
| 46 | + is also returned to use during iteration. |
| 47 | +\end{funcdesc} |
| 48 | + |
| 49 | + |
| 50 | +The following functions use the global state created by |
| 51 | +\function{input()}; if there is no active state, |
| 52 | +\exception{RuntimeError} is raised. |
| 53 | + |
| 54 | +\begin{funcdesc}{filename}{} |
| 55 | + Return the name of the file currently being read. Before the first |
| 56 | + line has been read, returns \code{None}. |
| 57 | +\end{funcdesc} |
| 58 | + |
| 59 | +\begin{funcdesc}{lineno}{} |
| 60 | + Return the cumulative line number of the line that has just been |
| 61 | + read. Before the first line has been read, returns \code{0}. After |
| 62 | + the last line of the last file has been read, returns the line |
| 63 | + number of that line. |
| 64 | +\end{funcdesc} |
| 65 | + |
| 66 | +\begin{funcdesc}{filelineno}{} |
| 67 | + Return the line number in the current file. Before the first line |
| 68 | + has been read, returns \code{0}. After the last line of the last |
| 69 | + file has been read, returns the line number of that line within the |
| 70 | + file. |
| 71 | +\end{funcdesc} |
| 72 | + |
| 73 | +\begin{funcdesc}{isfirstline}{} |
| 74 | + Return true iff the line just read is the first line of its file. |
| 75 | +\end{funcdesc} |
| 76 | + |
| 77 | +\begin{funcdesc}{isstdin}{} |
| 78 | + Returns true iff the last line was read from \code{sys.stdin}. |
| 79 | +\end{funcdesc} |
| 80 | + |
| 81 | +\begin{funcdesc}{nextfile}{} |
| 82 | + Close the current file so that the next iteration will read the |
| 83 | + first line from the next file (if any); lines not read from the file |
| 84 | + will not count towards the cumulative line count. The filename is |
| 85 | + not changed until after the first line of the next file has been |
| 86 | + read. Before the first line has been read, this function has no |
| 87 | + effect; it cannot be used to skip the first file. After the last |
| 88 | + line of the last file has been read, this function has no effect. |
| 89 | +\end{funcdesc} |
| 90 | + |
| 91 | +\begin{funcdesc}{close}{} |
| 92 | + Close the sequence. |
| 93 | +\end{funcdesc} |
| 94 | + |
| 95 | + |
| 96 | +The class which implements the sequence behavior provided by the |
| 97 | +module is available for subclassing as well: |
| 98 | + |
| 99 | +\begin{classdesc}{FileInput}{\optional{files\optional{, |
| 100 | + inplace\optional{, backup}}}} |
| 101 | + Class \class{FileInput} is the implementation; its methods |
| 102 | + \method{filename()}, \method{lineno()}, \method{fileline()}, |
| 103 | + \method{isfirstline()}, \method{isstdin()}, \method{nextfile()} and |
| 104 | + \method{close()} correspond to the functions of the same name in the |
| 105 | + module. In addition it has a \method{readline()} method which |
| 106 | + returns the next input line, and a \method{__getitem__()} method |
| 107 | + which implements the sequence behavior. The sequence must be |
| 108 | + accessed in strictly sequential order; random access and |
| 109 | + \method{readline()} cannot be mixed. |
| 110 | +\end{classdesc} |
| 111 | + |
| 112 | +\strong{Optional in-place filtering:} if the keyword argument |
| 113 | +\code{\var{inplace}=1} is passed to \function{input()} or to the |
| 114 | +\class{FileInput} constructor, the file is moved to a backup file and |
| 115 | +standard output is directed to the input file. |
| 116 | +This makes it possible to write a filter that rewrites its input file |
| 117 | +in place. If the keyword argument \code{\var{backup}='.<some |
| 118 | +extension>'} is also given, it specifies the extension for the backup |
| 119 | +file, and the backup file remains around; by default, the extension is |
| 120 | +\code{'.bak'} and it is deleted when the output file is closed. In-place |
| 121 | +filtering is disabled when standard input is read. |
| 122 | + |
| 123 | +\strong{Caveat:} The current implementation does not work for MS-DOS |
| 124 | +8+3 filesystems. |
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