Best way to retrieve variable values from a text file

Question

Referring on this question  I have a similar -but not the same- problem    On my way  I ll have some text file  structured like   var a   home  var b   car  var c  15 5   And I need that python read the file and then create a variable named var a with value  home   and so on   Example    python stuff over here getVarFromFile filename   this is the function that im looking for print var b  output  car  as string print var c  output 15 5  as number    Is this possible  I mean  even keep the var type   Notice that I have the full freedom to the text file structure  I can use the format I like if the one I proposed isn t the best   EDIT  the ConfigParser can be a solution  but I don t like it so much  because in my script I ll have then to refer to the variables in the file with  config get  set    var name     But what I ll love is to refer to the variable directly  as I declared it in the python script     There is a way to import the file as a python dictionary   Oh  last thing  keep in mind that I don t know exactly how many variables would I have in the text file   Edit 2  I m very interested at stephan s JSON solution  because in that way the text file could be read simply with others languages  PHP  then via AJAX JavaScript  for example   but I fail in something while acting that solution    for the example  i dont load the file but create a var with the supposed file content file content     var a   4   var b    a string   mydict   dict file content   Error  ValueError  dictionary update sequence element  0 has length 1  2 is required file content 2      var a   4   var b    a string    mydict 2   dict json dump file content 2  True    Error   Traceback  most recent call last    File   lt pyshell 5 gt    line 1  in  lt module gt   mydict 2   dict json dump file content 2  True    File  C  Python26 lib json   init   py   line 181  in dump  fp write chunk   AttributeError   bool  object has no attribute  write    In what kind of issues can I fall with the JSON format  And  how can I read a JSON array in a text file  and transform it in a python dict   P S  I don t like the solution using  py files  I ll prefer  txt   inc   whatever is not restrictive to one language

User · Answer

The other solutions posted here didn t work for me  because     i just needed parameters from a file for a normal script import   didn t work for me  as i need a way to override them by choosing another file Just a file with a dict wasn t fine  as I needed comments in it    So I ended up using Configparser and globals   update    Test file    File parametertest cfg   Settings   Comments are no Problem test  True bla  False     Here neither   that neither   And that s my demo script   import ConfigParser  cfg   ConfigParser RawConfigParser   cfg read  parametertest cfg           Read file   print cfg getboolean  Settings   bla     Manual Way to acess them  par dict cfg items  Settings    for p in par      par p  par p  split     1  0  strip     To get rid of inline comments  globals   update par    Make them availible globally  print bla   It s just for a file with one section now  but that will be easy to adopt   Hope it will be helpful for someone

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Suppose that you have a file Called  test txt  with   a 1 251 b 2 65415 c 3 54 d 549 5645 e 4684 65489   And you want to find a variable  a b c d or e    ffile open  test txt   r   read    variable raw input  Wich is the variable you are looking for  n    ini ffile find variable   len variable  1  rest ffile ini   search enter rest find   n   number float rest  search enter    print  value   number

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What you want appear to want is the following  but this is NOT RECOMMENDED    gt  gt  gt  for line in open  dangerous txt            exec   s    s    tuple line split      1          gt  gt  gt  var a  home    This creates somewhat similar behavior to PHP s register globals and hence has the same security issues  Additionally  the use of exec that I showed allows arbitrary code execution  Only use this if you are absolutely sure that the contents of the text file can be trusted under all circumstances   You should really consider binding the variables not to the local scope  but to an object  and use a library that parses the file contents such that no code is executed  So  go with any of the other solutions provided here    Please note  I added this answer not as a solution  but as an explicit non-solution

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How reliable is your format  If the seperator is always exactly       the following works  If not  a comparatively simple regex should do the job   As long as you re working with fairly simple variable types  Python s eval function makes persisting variables to files surprisingly easy    The below gives you a dictionary  btw  which you mentioned was one of your prefered solutions    def read config filename       f   open filename      config dict          for lines in f          items   lines split       1          config dict items 0     eval items 1       return config dict

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A simple way of reading variables from a text file using the standard library    Get vars from conf file var      with open  quot myvars conf quot   as conf          for line in conf                  if  quot   quot  in line                          name  value   line split  quot   quot                           var name    str value  rstrip   globals   update var

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hbn s answer won t work out of the box if the file to load is in a subdirectory or is named with dashes   In such a case you may consider this alternative     exec open myconfig py  read     Or the simpler but deprecated in python3     execfile myconfig py    I guess Stephan202 s warning applies to both options  though  and maybe the loop on lines is safer

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Load your file with JSON or PyYAML into a dictionary the dict  see doc for JSON or PyYAML for this step  both can store data type  and add the dictionary to your globals dictionary  e g  using globals   update the dict    If you want it in a local dictionary instead  e g  inside a function   you can do it like this   for  n  v  in the dict items        exec   s  s     n  repr v      as long as it is safe to use exec  If not  you can use the dictionary directly

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You can treat your text file as a python module and load it dynamically using imp load source   import imp imp load source  name  pathname   file      Example      mydata txt var1    hi  var2    how are you   var3     1  elem1   2  elem2              In your script file def getVarFromFile filename       import imp     f   open filename      global data     data   imp load source  data       f      f close      path to  config  file getVarFromFile  c  mydata txt   print data var1 print data var2 print data var3

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Use ConfigParser   Your config    myvars  var a   home  var b   car  var c  15 5   Your python code   import ConfigParser  config   ConfigParser ConfigParser   config read  config ini   var a   config get  myvars    var a   var b   config get  myvars    var b   var c   config get  myvars    var c

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But what i ll love is to refer to the variable direclty  as i declared it in the python script     Assuming you re happy to change your syntax slightly  just use python and import the  config  module     myconfig py   var a    home  var b    car  var c   15 5   Then do   from myconfig import     And you can reference them by name in your current context

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If your data has a regular structure you can read a file in line by line and populate your favorite container  For example   Let s say your data has 3 variables  x  y  i    A file contains n of these data  each variable on its own line  3 lines per record   Here are two records    384 198 0 255 444 2   Here s how you read your file data into a list   Reading from text  so cast accordingly    data      try      with open dataFilename   r   as file            read data until end of file         x   file readline           while x                    x   int x strip         remove  n  cast as int              y   file readline               y   int y strip                 i   file readline               i   int i strip                 data append  x y i                x   file readline    except FileNotFoundError as e      print  File not found    e   return data

[python] Best way to retrieve variable values from a text file?

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