Barak, Ron wrote:
Hi,
I have a generator whose aim is to returns consecutive lines from a file
(the listing below is a simplified version).
However, as it is written now, the generator method changes the text
file pointer to end of file after first invocation.
Namely, the file pointer changes from 0 to 6623 on line 24.
It might be that the generator method of self.input_file is reading the
file a chunk at a time for efficiency even though it's yielding a line
at a time.
Can you suggest how the generator could be changed, so it will allow me
to get the current location in the file after each yield ?
Thanks,
Ron.
$ cat -n generator.py # listing without line numbers is below
1 #!/usr/bin/env python
2
3 import gzip
4 from Debug import _line as line
5
6 class LogStream():
7
8 def __init__(self, filename):
9 self.filename = filename
10 self.input_file = self.open_file(filename)
11
12 def open_file(self, in_file):
13 try:
14 f = gzip.GzipFile(in_file, "r")
15 f.readline()
16 except IOError:
17 f = open(in_file, "r")
18 f.readline()
19 f.seek(0)
20 return(f)
21
22 def line_generator(self):
23 print line()+".
self.input_file.tell()==",self.input_file.tell()
24 for line_ in self.input_file:
25 print line()+".
self.input_file.tell()==",self.input_file.tell()
26 yield line_.strip()
27
28
29 if __name__ == "__main__":
30
31 filename = "sac.log.50lines"
32 log_stream = LogStream(filename)
33 log_stream.input_file.seek(0)
34 line_generator = log_stream.line_generator()
35 line_ = line_generator.next()
$ python generator.py
23. self.input_file.tell()== 0
25. self.input_file.tell()== 6623
$ wc -c sac.log.50lines
6623 sac.log.50lines
$ cat generator.py
#!/usr/bin/env python
import gzip
from Debug import _line as line
class LogStream():
def __init__(self, filename):
self.filename = filename
self.input_file = self.open_file(filename)
def open_file(self, in_file):
try:
f = gzip.GzipFile(in_file, "r")
f.readline()
except IOError:
f = open(in_file, "r")
f.readline()
f.seek(0)
return(f)
def line_generator(self):
print line()+". self.input_file.tell()==",self.input_file.tell()
for line_ in self.input_file:
print line()+". self.input_file.tell()==",self.input_file.tell()
yield line_.strip()
if __name__ == "__main__":
filename = "sac.log.50lines"
log_stream = LogStream(filename)
log_stream.input_file.seek(0)
line_generator = log_stream.line_generator()
line_ = line_generator.next()
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