适用于偶数和奇数长度的文件。它只是忽略了不匹配的最后一行。
f=file("file")
lines = f.readlines()
for even, odd in zip(lines[0::2], lines[1::2]):
print "even : ", even
print "odd : ", odd
print "end cycle"
f.close()
如果您有大文件，这不是正确的方法。您正在使用 readlines() 加载内存中的所有文件。我曾经写过一个类，它读取保存每个行首的 fseek 位置的文件。这使您无需将所有文件都放在内存中即可获取特定行，并且您还可以前进和后退。
我把它贴在这里。许可证是公共领域，意思是，用它做你想做的事。请注意，这门课是 6 年前写的，从那以后我就没有碰过或检查过它。我认为它甚至不符合文件要求。 告诫购买者。另外，请注意，这对您的问题来说太过分了。我并不是说你绝对应该这样做，但我有这段代码，如果你需要更复杂的访问，我很乐意分享它。
import string
import re
class FileReader:
"""
Similar to file class, but allows to access smoothly the lines
as when using readlines(), with no memory payload, going back and forth,
finding regexps and so on.
"""
def __init__(self,filename): # fold>>
self.__file=file(filename,"r")
self.__currentPos=-1
# get file length
self.__file.seek(0,0)
counter=0
line=self.__file.readline()
while line != '':
counter = counter + 1
line=self.__file.readline()
self.__length = counter
# collect an index of filedescriptor positions against
# the line number, to enhance search
self.__file.seek(0,0)
self.__lineToFseek = []
while True:
cur=self.__file.tell()
line=self.__file.readline()
# if it's not null the cur is valid for
# identifying a line, so store
self.__lineToFseek.append(cur)
if line == '':
break
# <<fold
def __len__(self): # fold>>
"""
member function for the operator len()
returns the file length
FIXME: better get it once when opening file
"""
return self.__length
# <<fold
def __getitem__(self,key): # fold>>
"""
gives the "key" line. The syntax is
import FileReader
f=FileReader.FileReader("a_file")
line=f[2]
to get the second line from the file. The internal
pointer is set to the key line
"""
mylen = self.__len__()
if key < 0:
self.__currentPos = -1
return ''
elif key > mylen:
self.__currentPos = mylen
return ''
self.__file.seek(self.__lineToFseek[key],0)
counter=0
line = self.__file.readline()
self.__currentPos = key
return line
# <<fold
def next(self): # fold>>
if self.isAtEOF():
raise StopIteration
return self.readline()
# <<fold
def __iter__(self): # fold>>
return self
# <<fold
def readline(self): # fold>>
"""
read a line forward from the current cursor position.
returns the line or an empty string when at EOF
"""
return self.__getitem__(self.__currentPos+1)
# <<fold
def readbackline(self): # fold>>
"""
read a line backward from the current cursor position.
returns the line or an empty string when at Beginning of
file.
"""
return self.__getitem__(self.__currentPos-1)
# <<fold
def currentLine(self): # fold>>
"""
gives the line at the current cursor position
"""
return self.__getitem__(self.__currentPos)
# <<fold
def currentPos(self): # fold>>
"""
return the current position (line) in the file
or -1 if the cursor is at the beginning of the file
or len(self) if it's at the end of file
"""
return self.__currentPos
# <<fold
def toBOF(self): # fold>>
"""
go to beginning of file
"""
self.__getitem__(-1)
# <<fold
def toEOF(self): # fold>>
"""
go to end of file
"""
self.__getitem__(self.__len__())
# <<fold
def toPos(self,key): # fold>>
"""
go to the specified line
"""
self.__getitem__(key)
# <<fold
def isAtEOF(self): # fold>>
return self.__currentPos == self.__len__()
# <<fold
def isAtBOF(self): # fold>>
return self.__currentPos == -1
# <<fold
def isAtPos(self,key): # fold>>
return self.__currentPos == key
# <<fold
def findString(self, thestring, count=1, backward=0): # fold>>
"""
find the count occurrence of the string str in the file
and return the line catched. The internal cursor is placed
at the same line.
backward is the searching flow.
For example, to search for the first occurrence of "hello
starting from the beginning of the file do:
import FileReader
f=FileReader.FileReader("a_file")
f.toBOF()
f.findString("hello",1,0)
To search the second occurrence string from the end of the
file in backward movement do:
f.toEOF()
f.findString("hello",2,1)
to search the first occurrence from a given (or current) position
say line 150, going forward in the file
f.toPos(150)
f.findString("hello",1,0)
return the string where the occurrence is found, or an empty string
if nothing is found. The internal counter is placed at the corresponding
line number, if the string was found. In other case, it's set at BOF
if the search was backward, and at EOF if the search was forward.
NB: the current line is never evaluated. This is a feature, since
we can so traverse occurrences with a
line=f.findString("hello")
while line == '':
line.findString("hello")
instead of playing with a readline every time to skip the current
line.
"""
internalcounter=1
if count < 1:
count = 1
while 1:
if backward == 0:
line=self.readline()
else:
line=self.readbackline()
if line == '':
return ''
if string.find(line,thestring) != -1 :
if count == internalcounter:
return line
else:
internalcounter = internalcounter + 1
# <<fold
def findRegexp(self, theregexp, count=1, backward=0): # fold>>
"""
find the count occurrence of the regexp in the file
and return the line catched. The internal cursor is placed
at the same line.
backward is the searching flow.
You need to pass a regexp string as theregexp.
returns a tuple. The fist element is the matched line. The subsequent elements
contains the matched groups, if any.
If no match returns None
"""
rx=re.compile(theregexp)
internalcounter=1
if count < 1:
count = 1
while 1:
if backward == 0:
line=self.readline()
else:
line=self.readbackline()
if line == '':
return None
m=rx.search(line)
if m != None :
if count == internalcounter:
return (line,)+m.groups()
else:
internalcounter = internalcounter + 1
# <<fold
def skipLines(self,key): # fold>>
"""
skip a given number of lines. Key can be negative to skip
backward. Return the last line read.
Please note that skipLines(1) is equivalent to readline()
skipLines(-1) is equivalent to readbackline() and skipLines(0)
is equivalent to currentLine()
"""
return self.__getitem__(self.__currentPos+key)
# <<fold
def occurrences(self,thestring,backward=0): # fold>>
"""
count how many occurrences of str are found from the current
position (current line excluded... see skipLines()) to the
begin (or end) of file.
returns a list of positions where each occurrence is found,
in the same order found reading the file.
Leaves unaltered the cursor position.
"""
curpos=self.currentPos()
list = []
line = self.findString(thestring,1,backward)
while line != '':
list.append(self.currentPos())
line = self.findString(thestring,1,backward)
self.toPos(curpos)
return list
# <<fold
def close(self): # fold>>
self.__file.close()
# <<fold