如何在python中的文本文件中对行进行排序并选择其中的某些字符？

Question

The lines of my text file are:

<< end of ENERGY.
iupac_m_486_> OE1/2 will be swapped:     -136.1396        1     1
openf___224_> Open           Dominio1.BL00100001.pdb
wrpdb___568_> Residues, atoms, selected atoms:      268     2115     2115

>> Summary of successfully produced loop models:
Filename                          molpdf
----------------------------------------
Dominio1.BL00010001.pdb         24.69530
Dominio1.BL00020001.pdb         14.33748
Dominio1.BL00030001.pdb         30.53454
Dominio1.BL00040001.pdb         23.82516
Dominio1.BL00050001.pdb         27.48684
Dominio1.BL00060001.pdb         18.17364
Dominio1.BL00070001.pdb         30.98407
Dominio1.BL00080001.pdb         17.19927
Dominio1.BL00090001.pdb         19.02460
Dominio1.BL00100001.pdb         22.57086

I want to create a code that selects the number line (last 10 lines)that has the smallest number (identify),and read the name of the .pdb (just the 24 characters of the line that has the smallest number).Cause, I need identify what's the .pdb that has the smallest number, and use it like a string in other script, like this:

model='%s'%R

where '%s'%R is the name of .pdb that i need

How can I do it?

Answer 1

You need to use min function with a proper key :

>>> min(s.split('\n\n'),key=lambda x:float(x.split()[-1])).split()[0]
'Dominio1.BL00020001.pdb'

Demo :

>>> s="""Dominio1.BL00010001.pdb 24.69530
... 
... Dominio1.BL00020001.pdb 14.33748
... 
... Dominio1.BL00030001.pdb 30.53454
... 
... Dominio1.BL00040001.pdb 23.82516
... 
... Dominio1.BL00050001.pdb 27.48684
... 
... Dominio1.BL00060001.pdb 18.17364
... 
... Dominio1.BL00070001.pdb 30.98407
... 
... Dominio1.BL00080001.pdb 17.19927
... 
... Dominio1.BL00090001.pdb 19.02460
... 
... Dominio1.BL00100001.pdb 22.57086"""

>>> min(s.split('\n\n'),key=lambda x:float(x.split()[-1]))
'Dominio1.BL00020001.pdb 14.33748'
>>> min(s.split('\n\n'),key=lambda x:float(x.split()[-1])).split()[0]
'Dominio1.BL00020001.pdb'

Answer 2

A normal file read operation will do

data = file.readlines()
pdb_files = []
float_values = []
for line in data:
    pdb,float_value = line.split()
    pdb_files.append(pdb)
    float_values.append(float(float_value))
min_float_index = float_values.indexof(min(float_values))
print pdb_files.index(min_float_index)

This code stores the data in two lists, and finds the least of the float values given. Then prints the corresponding entry of the pdb filename

Answer 3

Try this:

def get_minimal_value_entry(file_name):
    with open(file_name, 'r') as f:

        # the value of a  line is the second member of 'split' result
        key = lambda x: float(x.strip().split()[1])

        return min(f, key=key).split()[0]

# 'test' file holds the data...
print get_minimal_value_entry('test')

# prints Dominio1.BL00020001.pdb

If you have empty lines use itertools.ifilter to filter empty lines:

from itertools import ifilter

def get_minimal_value_entry(file_name):
    with open(file_name, 'r') as f:

        # the value of a  line is the second member of 'split' result
        key = lambda x: float(x.strip().split()[1])

        return min(ifilter(lambda x: x.split(), f), key=key).split()[0]

# 'test' file holds the data...
print get_minimal_value_entry('test')

# prints Dominio1.BL00020001.pdb

Answer 4

I'd use Python re .

file.txt

Dominio1.BL00010001.pdb    24.69530

Dominio1.BL00020001.pdb    14.33748

Dominio1.BL00030001.pdb    30.53454

Dominio1.BL00040001.pdb    23.82516

Dominio1.BL00050001.pdb    27.48684

Dominio1.BL00060001.pdb    18.17364

Dominio1.BL00070001.pdb    30.98407

Dominio1.BL00080001.pdb    17.19927

Dominio1.BL00090001.pdb    19.02460

Dominio1.BL00100001.pdb    22.57086

sorts.py

import re

lines = open('file.txt').readlines() # readlines
lines = [i.strip() for i in lines] # remove newlines

lines = [re.sub('\s+', ' ', i) for i in lines] # remove extra spaces
lines = [i.split(' ') for i in lines] # split by space

lines = [i for i in lines if i != ['']] # remove empty lines
lines = sorted(lines, key = lambda i: float(i[1])) # sort by id

print lines[0][0] # print item with least id