Question: i have a file with information in the pattern of:

```
.343423 1
.434322 1
.453434 1
.534342 1

```

Equal size each line and row in sorted order..I have a variable "a" with a value and need to get the row number which it closest to "a" comparing with the values in the 1st column..

Till now i was coping the 1st column element into list and then using bisect method i am getting the row\_num...but as i need to perform this many times..this has become painfully slow as i need to copy some 4000 element to list everytime..

so now i am thinking of doing it with dict instead of datastructure as i would be faster...but i dont know whether we can use dict in bisect if possible how can we use for this case please suggest...
if not possible are they any method for loading data into list faster then normal???
thanking you...

Answer: 
Similar to Dave Kirby's solution, consider the [sortedcontainers](http://www.grantjenks.com/docs/sortedcontainers/) module on [PyPI](https://pypi.python.org/pypi/sortedcontainers). It's pure-Python, [fast](http://www.grantjenks.com/docs/sortedcontainers/performance.html), and provides a [SortedDict type with bisect](http://www.grantjenks.com/docs/sortedcontainers/sorteddict.html#sortedcontainers.SortedDict.d.bisect_left) over the keys. It's also a lot faster than a balanced binary tree type for bulk-loading data from a file.

In your case, something like this might work:

```
from sortedcontainers import SortedDict
with open('data.txt') as fptr:
    sd = SortedDict(map(int, line[1:].split()) for line in fptr)

# sd now contains key, value pairs corresponding to the columns in your data file
# Lookup index of desired key:

pos = sd.bisect(434323)

# pos points to the index of the key 434322
# get that key:

key = sd.iloc[pos]

# now get the value:

value = sd[key]

```

The operations: bisecting, indexing, and key lookup are all very fast within the sortedcontainers module. This solution requires that you can keep the entire contents of the file in memory.
Here is a way to use `bisect` without reading the entire file. The OS will end up reading much more of the file than you need regardless, so you won't see a performance gain until `data.txt` big enough

```
from os import SEEK_END
from bisect import bisect

class ListProxy(object):
    def __init__(self, f):
        self.f = f
        self.line_len = len(f.readline())
        self.f.seek(0, SEEK_END)
        self.num_lines = self.f.tell()//self.line_len

    def __len__(self):
        return self.num_lines

    def __getitem__(self, idx):
        self.f.seek(idx*self.line_len)
        return float(self.f.read(7))

with open("data.txt") as f:
    lp = ListProxy(f)    
    num = .44
    idx = bisect(lp, num)
    if idx != 0 and num - lp[idx-1] < lp[idx] - num:
        idx -=1
    print num, idx

```