summaryrefslogtreecommitdiffstats
path: root/Lib/fileinput.py
blob: c18995b6b33bbcb240ac6a8596e8dfc502d5b318 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
"""Helper class to quickly write a loop over all standard input files.

Typical use is:

    import fileinput
    for line in fileinput.input():
        process(line)

This iterates over the lines of all files listed in sys.argv[1:],
defaulting to sys.stdin if the list is empty.  If a filename is '-' it
is also replaced by sys.stdin.  To specify an alternative list of
filenames, pass it as the argument to input().  A single file name is
also allowed.

Functions filename(), lineno() return the filename and cumulative line
number of the line that has just been read; filelineno() returns its
line number in the current file; isfirstline() returns true iff the
line just read is the first line of its file; isstdin() returns true
iff the line was read from sys.stdin.  Function nextfile() closes the
current file so that the next iteration will read the first line from
the next file (if any); lines not read from the file will not count
towards the cumulative line count; the filename is not changed until
after the first line of the next file has been read.  Function close()
closes the sequence.

Before any lines have been read, filename() returns None and both line
numbers are zero; nextfile() has no effect.  After all lines have been
read, filename() and the line number functions return the values
pertaining to the last line read; nextfile() has no effect.

All files are opened in text mode.  If an I/O error occurs during
opening or reading a file, the IOError exception is raised.

If sys.stdin is used more than once, the second and further use will
return no lines, except perhaps for interactive use, or if it has been
explicitly reset (e.g. using sys.stdin.seek(0)).

Empty files are opened and immediately closed; the only time their
presence in the list of filenames is noticeable at all is when the
last file opened is empty.

It is possible that the last line of a file doesn't end in a newline
character; otherwise lines are returned including the trailing
newline.

Class FileInput is the implementation; its methods filename(),
lineno(), fileline(), isfirstline(), isstdin(), nextfile() and close()
correspond to the functions in the module.  In addition it has a
readline() method which returns the next input line, and a
__getitem__() method which implements the sequence behavior.  The
sequence must be accessed in strictly sequential order; sequence
access and readline() cannot be mixed.

Optional in-place filtering: if the keyword argument inplace=1 is
passed to input() or to the FileInput constructor, the file is moved
to a backup file and standard output is directed to the input file.
This makes it possible to write a filter that rewrites its input file
in place.  If the keyword argument backup=".<some extension>" is also
given, it specifies the extension for the backup file, and the backup
file remains around; by default, the extension is ".bak" and it is
deleted when the output file is closed.  In-place filtering is
disabled when standard input is read.  XXX The current implementation
does not work for MS-DOS 8+3 filesystems.

Performance: this module is unfortunately one of the slower ways of
processing large numbers of input lines.  Nevertheless, a significant
speed-up has been obtained by using readlines(bufsize) instead of
readline().  A new keyword argument, bufsize=N, is present on the
input() function and the FileInput() class to override the default
buffer size.

XXX Possible additions:

- optional getopt argument processing
- specify open mode ('r' or 'rb')
- fileno()
- isatty()
- read(), read(size), even readlines()

"""

import sys, os, stat

__all__ = ["input","close","nextfile","filename","lineno","filelineno",
           "isfirstline","isstdin","FileInput"]

_state = None

DEFAULT_BUFSIZE = 8*1024

def input(files=None, inplace=0, backup="", bufsize=0):
    global _state
    if _state and _state._file:
        raise RuntimeError, "input() already active"
    _state = FileInput(files, inplace, backup, bufsize)
    return _state

def close():
    global _state
    state = _state
    _state = None
    if state:
        state.close()

def nextfile():
    if not _state:
        raise RuntimeError, "no active input()"
    return _state.nextfile()

def filename():
    if not _state:
        raise RuntimeError, "no active input()"
    return _state.filename()

def lineno():
    if not _state:
        raise RuntimeError, "no active input()"
    return _state.lineno()

def filelineno():
    if not _state:
        raise RuntimeError, "no active input()"
    return _state.filelineno()

def isfirstline():
    if not _state:
        raise RuntimeError, "no active input()"
    return _state.isfirstline()

def isstdin():
    if not _state:
        raise RuntimeError, "no active input()"
    return _state.isstdin()

class FileInput:

    def __init__(self, files=None, inplace=0, backup="", bufsize=0):
        if type(files) == type(''):
            files = (files,)
        else:
            if files is None:
                files = sys.argv[1:]
            if not files:
                files = ('-',)
            else:
                files = tuple(files)
        self._files = files
        self._inplace = inplace
        self._backup = backup
        self._bufsize = bufsize or DEFAULT_BUFSIZE
        self._savestdout = None
        self._output = None
        self._filename = None
        self._lineno = 0
        self._filelineno = 0
        self._file = None
        self._isstdin = 0
        self._backupfilename = None
        self._buffer = []
        self._bufindex = 0

    def __del__(self):
        self.close()

    def close(self):
        self.nextfile()
        self._files = ()

    def __getitem__(self, i):
        try:
            line = self._buffer[self._bufindex]
        except IndexError:
            pass
        else:
            self._bufindex += 1
            self._lineno += 1
            self._filelineno += 1
            return line
        if i != self._lineno:
            raise RuntimeError, "accessing lines out of order"
        line = self.readline()
        if not line:
            raise IndexError, "end of input reached"
        return line

    def nextfile(self):
        savestdout = self._savestdout
        self._savestdout = 0
        if savestdout:
            sys.stdout = savestdout

        output = self._output
        self._output = 0
        if output:
            output.close()

        file = self._file
        self._file = 0
        if file and not self._isstdin:
            file.close()

        backupfilename = self._backupfilename
        self._backupfilename = 0
        if backupfilename and not self._backup:
            try: os.unlink(backupfilename)
            except: pass

        self._isstdin = 0
        self._buffer = []
        self._bufindex = 0

    def readline(self):
        try:
            line = self._buffer[self._bufindex]
        except IndexError:
            pass
        else:
            self._bufindex += 1
            self._lineno += 1
            self._filelineno += 1
            return line
        if not self._file:
            if not self._files:
                return ""
            self._filename = self._files[0]
            self._files = self._files[1:]
            self._filelineno = 0
            self._file = None
            self._isstdin = 0
            self._backupfilename = 0
            if self._filename == '-':
                self._filename = '<stdin>'
                self._file = sys.stdin
                self._isstdin = 1
            else:
                if self._inplace:
                    self._backupfilename = (
                        self._filename + (self._backup or os.extsep+"bak"))
                    try: os.unlink(self._backupfilename)
                    except os.error: pass
                    # The next few lines may raise IOError
                    os.rename(self._filename, self._backupfilename)
                    self._file = open(self._backupfilename, "r")
                    try:
                        perm = os.fstat(self._file.fileno())[stat.ST_MODE]
                    except:
                        self._output = open(self._filename, "w")
                    else:
                        fd = os.open(self._filename,
                                     os.O_CREAT | os.O_WRONLY | os.O_TRUNC,
                                     perm)
                        self._output = os.fdopen(fd, "w")
                        try:
                            os.chmod(self._filename, perm)
                        except:
                            pass
                    self._savestdout = sys.stdout
                    sys.stdout = self._output
                else:
                    # This may raise IOError
                    self._file = open(self._filename, "r")
        self._buffer = self._file.readlines(self._bufsize)
        self._bufindex = 0
        if not self._buffer:
            self.nextfile()
        # Recursive call
        return self.readline()

    def filename(self):
        return self._filename

    def lineno(self):
        return self._lineno

    def filelineno(self):
        return self._filelineno

    def isfirstline(self):
        return self._filelineno == 1

    def isstdin(self):
        return self._isstdin

def _test():
    import getopt
    inplace = 0
    backup = 0
    opts, args = getopt.getopt(sys.argv[1:], "ib:")
    for o, a in opts:
        if o == '-i': inplace = 1
        if o == '-b': backup = a
    for line in input(args, inplace=inplace, backup=backup):
        if line[-1:] == '\n': line = line[:-1]
        if line[-1:] == '\r': line = line[:-1]
        print "%d: %s[%d]%s %s" % (lineno(), filename(), filelineno(),
                                   isfirstline() and "*" or "", line)
    print "%d: %s[%d]" % (lineno(), filename(), filelineno())

if __name__ == '__main__':
    _test()