How to read numbers from file in Python

Question

I d like to read numbers from file into two dimensional array    File contents    line containing w  h h lines containing w integers separated with space   For example   4 3 1 2 3 4 2 3 4 5 6 7 8 9

User · Answer

Not sure why do you need w h  If these values are actually required and mean that only specified number of rows and cols should be read than you can try the following   output      with open r c  file txt    r   as f      w  h    map int  f readline   split        tmp          for i  line in enumerate f           if i    h              break         tmp append map int  line split    w        output append tmp

User · Answer

Assuming you don t have extraneous whitespace   with open  file   as f      w  h    int x  for x in next f  split      read first line     array          for line in f    read rest of lines         array append  int x  for x in line split       You could condense the last for loop into a nested list comprehension   with open  file   as f      w  h    int x  for x in next f  split        array     int x  for x in line split    for line in f

User · Answer

is working with both python2 e g  Python 2 7 10  and python3 e g  Python 3 6 4   with open  in txt   as f    rows cols np fromfile f  dtype int  count 2  sep        data   np fromfile f  dtype int  count cols rows  sep      reshape  rows cols     another way  is working with both python2 e g  Python 2 7 10  and python3 e g  Python 3 6 4   as well for complex matrices see the example below  only change int to complex   with open  in txt   as f     data         cols rows list map int  f readline   split        for i in range 0  rows         data append list map int  f readline   split    cols     print  data    I updated the code  this method is working for any number of matrices and any kind of matrices int complex float  in the initial in txt file   This program yields matrix multiplication as an application  Is working with python2  in order to work with python3 make the following changes  print to print     and  print   7g   a i j      to     print    7g   a i j  end       the script   import numpy as np  def printMatrix a      print   Matrix      d   a shape 0           d   a shape 1           rows   a shape 0     cols   a shape 1     for i in range 0 rows         for j in range 0 cols            print   7g   a i j         print    print        def readMatrixFile FileName      rows cols np fromfile FileName  dtype int  count 2  sep         a   np fromfile FileName  dtype float  count rows cols  sep      reshape  rows cols      return a  def readMatrixFileComplex FileName      data         rows cols list map int  FileName readline   split        for i in range 0  rows         data append list map complex  FileName readline   split    cols        a   np array data     return a  f   open  in txt   a readMatrixFile f  printMatrix a  b readMatrixFile f  printMatrix b  a1 readMatrixFile f  printMatrix a1  b1 readMatrixFile f  printMatrix b1  f close    print   matrix multiplication   c   np dot a b  printMatrix c  c1   np dot a1 b1  printMatrix c1   with open  complex in txt   as fid    a2 readMatrixFileComplex fid    print a2    b2 readMatrixFileComplex fid    print b2   print   complex matrix multiplication   c2   np dot a2 b2  print c2  print   real part of complex matrix   printMatrix c2 real  print   imaginary part of complex matrix   printMatrix c2 imag    as input file I take  in txt   4 4 1 1 1 1 2 4 8 16 3 9 27 81 4 16 64 256 4 3 4 02 -3 0 4 0 -13 0 19 0 -7 0 3 0 -2 0 7 0 -1 0 1 0 -1 0 3 4 1 2 -2 0 -3 4 7 2 6 0 3 1 4 2 -1 3 0 9 1 -11 4 -5   and complex in txt  3 4 1 1j 2 2j -2-2j 0 0j -3-3j 4 4j 7 7j 2 2j 6 6j 0 0j 3 3j 1 1j 4 2 -1-1j 3 3j 0 0j 9 9j 1 1j -11-11j 4 4j -5-5j   and the output look like   Matrix 4  4       1      1      1      1      2      4      8     16      3      9     27     81      4     16     64    256  Matrix 4  3    4 02     -3      4    -13     19     -7      3     -2      7     -1      1     -1  Matrix 3  4       1      2     -2      0     -3      4      7      2      6      0      3      1  Matrix 4  2      -1      3      0      9      1    -11      4     -5  matrix multiplication Matrix 4  3    -6 98      15       3  -35 96      70      20 -104 94     189      57 -255 92     420      96  Matrix 3  2      -3     43     18    -60      1    -20     1  1 j  2  2 j -2 -2 j  0  0 j    -3 -3 j  4  4 j  7  7 j  2  2 j     6  6 j  0  0 j  3  3 j  1  1 j      -1  -1 j   3   3 j      0   0 j   9   9 j      1   1 j -11 -11 j      4   4 j  -5  -5 j   complex matrix multiplication    0   -6 j  0   86 j     0   36 j  0 -120 j     0    2 j  0  -40 j   real part of complex matrix Matrix 3  2        0       0       0       0       0       0  imaginary part of complex matrix Matrix 3  2       -6      86      36    -120       2     -40

User · Answer

To me this kind of seemingly simple problem is what Python is all about  Especially if you re coming from a language like C    where simple text parsing can be a pain in the butt  you ll really appreciate the functionally unit-wise solution that python can give you  I d keep it really simple with a couple of built-in functions and some generator expressions   You ll need open name  mode   myfile readlines    mystring split    int myval   and then you ll probably want to use a couple of generators to put them all together in a pythonic way     This opens a handle to your file  in  r  read mode file handle   open  mynumbers txt    r     Read in all the lines of your file into a list of lines lines list   file handle readlines     Extract dimensions from first line  Cast values to integers from strings  cols  rows    int val  for val in lines list 0  split      Do a double-nested list comprehension to get the rest of the data into your matrix my data     int val  for val in line split    for line in lines list 1      Look up generator expressions here  They can really simplify your code into discrete functional units  Imagine doing the same thing in 4 lines in C      It would be a monster  Especially the list generators  when I was I C   guy I always wished I had something like that  and I d often end up building custom functions to construct each kind of array I wanted

User · Answer

To make the answer simple here is a program that reads integers from the file and sorting them  f   open  input txt    r    nums   f readlines   nums    int i  for i in nums    After reading each line of the file converting each string to a digit  nums sort     Sorting the numbers  f close    f   open  input txt    w   for num in nums      f write   d n   num   f close     Writing them back As easy as that  Hope this helps

[python] How to read numbers from file in Python?

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