Python: read one word per line of a text file - file

Question

Its not a proper code but I want to know if there is a way to search just one word w./o using .split() as it forms a list and i dont want that with this snippet:
f=(i for i in fin.xreadlines())
for i in f:
try:
match=re.search(r"([A-Z]+\b) | ([A-Z\'w]+\b) | (\b[A-Z]+\b) | (\b[A-Z\'w]+\b) | (.\w+\b)", i) # | r"[A-Z\'w]+\b" | r"\b[A-Z]+\b" | r"\b[A-Z\'w]+\b" | r".\w+\b"
Also can i make a reusable class module like this
class LineReader: #Intended only to be used with for loop
def __init__(self,filename):
self.fin=open(filename,'r')
def __getitem__(self,index):
line=self.fin.xreadline()
return line.split()
where say f=LineReader(filepath)
and for i in f.getitem(index=line number 25) loop starts from there?
i dont know how to do that.any tips?

Answer 1

To get the first word of a line:
line[:max(line.find(' '), 0) or None]
line.find(' ') searches for the first whitespace, and returns it. If there is no whitespace found it returns -1
max( ... ), 0) makes sure the result is always greater than 0, and makes -1 0. This is usefull because bool(-1) is True and bool(0) is False.
x or None evaluates to x if x != 0 else None
and finaly line[:None] is equal to line[:], which returns a string identical to line
First sample:
with open('file') as f:
for line in f:
word = line[:max(line.find(' '), 0) or None]
if condition(word):
do_something(word)
And the class (implemented as a generator here)
def words(stream):
for line in stream:
yield line[:max(line.find(' '), 0) or None]
Which you could use like
gen = words(f)
for word in gen:
if condition(word):
print word
Or
gen = words(f)
while 1:
try:
word = gen.next()
if condition(word):
print word
except StopIteration:
break # we reached the end
But you also wanted to start reading from a certain linenumber. This can't be done very efficient if you don't know the lengths of the lines. The only way is reading lines and discarding them until you reach the right linenumber.
def words(stream, start=-1): # you could replace the -1 with 0 and remove the +1
for i in range(start+1): # it depend on whether you start counting with 0 or 1
try:
stream.next()
except StopIteration:
break
for line in stream:
yield line[:max(line.find(' '), 0) or None]
Be aware that you could get strange results if a line would start with a space. To prevent that, you could insert line = line.rstrip() at the beginning of the loop.
Disclaimer: None of this code is tested