More elegant way of declaring multiple variables at the same time

Question

To declare multiple variables at the  same time  I would do   a  b   True  False   But if I had to declare much more variables  it turns less and less elegant   a  b  c  d  e  f  g  h  i  j   True  True  True  True  True  False  True  True   True  True   Is there a better   elegant   convenient way to do this   This must be very basic  but if I do used a list or a tuple for storing the variables  how would I have to approach so that I would be helpful since   aList    a b    Is not valid  I would have to do   a  b   True  True   Or what am I missing

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Like JavaScript you can also use multiple statements on one line in python a   1  b    Hello World   c    3

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As others have suggested  it s unlikely that using 10 different local variables with Boolean values is the best way to write your routine  especially if they really have one-letter names     Depending on what you re doing  it may make sense to use a dictionary instead   For example  if you want to set up Boolean preset values for a set of one-letter flags  you could do this    gt  gt  gt  flags   dict fromkeys   a    b    c    True   gt  gt  gt  flags update dict fromkeys   d    e    False    gt  gt  gt  print flags   a   True   c   True   b   True   e   False   d   False      If you prefer  you can also do it with a single assignment statement    gt  gt  gt  flags   dict dict fromkeys   a    b    c    True                      dict fromkeys   d    e    False    gt  gt  gt  print flags   a   True   c   True   b   True   e   False   d   False    The second parameter to dict isn t entirely designed for this  it s really meant to allow you to override individual elements of the dictionary using keyword arguments like d False   The code above blows up the result of the expression following    into a set of keyword arguments which are passed to the called function   This is certainly a reliable way to create dictionaries  and people seem to be at least accepting of this idiom  but I suspect that some may consider it Unpythonic    lt  disclaimer gt     Yet another approach  which is likely the most intuitive if you will be using this pattern frequently  is to define your data as a list of flag values  True  False  mapped to flag names  single-character strings    You then transform this data definition into an inverted dictionary which maps flag names to flag values   This can be done quite succinctly with a nested list comprehension  but here s a very readable implementation    gt  gt  gt  def invert dict inverted dict           elements   inverted dict iteritems           for flag value  flag names in elements              for flag name in flag names                  yield flag name  flag value       gt  gt  gt  flags    True    a    b    c    False    d    e     gt  gt  gt  flags   dict invert dict flags    gt  gt  gt  print flags   a   True   c   True   b   True   e   False   d   False    The function invert dict is a generator function   It generates  or yields     meaning that it repeatedly returns values of     key-value pairs   Those key-value pairs are the inverse of the contents of the two elements of the initial flags dictionary   They are fed into the dict constructor   In this case the dict constructor works differently from above because it s being fed an iterator rather than a dictionary as its argument     Drawing on  Chris Lutz s comment  If you will really be using this for single-character values  you can actually do   gt  gt  gt  flags    True   abc   False   de    gt  gt  gt  flags   dict invert dict flags    gt  gt  gt  print flags   a   True   c   True   b   True   e   False   d   False    This works because Python strings are iterable  meaning that they can be moved through value by value   In the case of a string  the values are the individual characters in the string   So when they are being interpreted as iterables  as in this case where they are being used in a for loop    a    b    c   and  abc  are effectively equivalent   Another example would be when they are being passed to a function that takes an iterable  like tuple   I personally wouldn t do this because it doesn t read intuitively  when I see a string  I expect it to be used as a single value rather than as a list   So I look at the first line and think  Okay  so there s a True flag and a False flag    So although it s a possibility  I don t think it s the way to go   On the upside  it may help to explain the concepts of iterables and iterators more clearly     Defining the function invert dict such that it actually returns a dictionary is not a bad idea either  I mostly just didn t do that because it doesn t really help to explain how the routine works     Apparently Python 2 7 has dictionary comprehensions  which would make for an extremely concise way to implement that function   This is left as an exercise to the reader  since I don t have Python 2 7 installed     You can also combine some functions from the ever-versatile itertools module   As they say  There s More Than One Way To Do It   Wait  the Python people don t say that   Well  it s true anyway in some cases   I would guess that Guido hath given unto us dictionary comprehensions so that there would be One Obvious Way to do this

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I like the top voted answer  however  it has problems with list as shown      gt  gt  a  b     0  5   2    gt  gt  print b    0  0  0  0  0     gt  gt  a 0    1    gt  gt  print b    1  0  0  0  0    This is discussed in great details  here   but the gist is that a and b are the same object with a is b returning True  same for id a     id b    Therefore if you change an index  you are changing the index of both a and b  since they are linked  To solve this you can do  source    gt  gt  a  b     0  5 for i in range 2    gt  gt  print b  0  0  0  0  0   gt  gt  a 0    1  gt  gt  print b  0  0  0  0  0      This can then be used as a variant of the top answer  which has the  desired  intuitive results   gt  gt  a  b  c  d  e  g  h  i    True for i in range 9    gt  gt  f    False for i in range 1    to be pedantic

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This is an elaboration on  Jeff M s and my comments   When you do this   a  b   c  d   It works with tuple packing and unpacking  You can separate the packing and unpacking steps       c  d a  b       The first line creates a tuple called   which has two elements  the first with the value of c and the second with the value of d  The second line unpacks the   tuple into the variables a and b  This breaks down your one huge line   a  b  c  d  e  f  g  h  i  j   True  True  True  True  True  False  True  True  True  True   Into two smaller lines       True  True  True  True  True  False  True  True  True  True a  b  c  d  e  f  g  h  i  j       It will give you the exact same result as the first line  including the same exception if you add values or variables to one part but forget to update the other    However  in this specific case  yan s answer is perhaps the best   If you have a list of values  you can still unpack them  You just have to convert it to a tuple first  For example  the following will assign a value between 0 and 9 to each of a through j  respectively   a  b  c  d  e  f  g  h  i  j   tuple range 10     EDIT  Neat trick to assign all of them as true except element 5  variable f    a  b  c  d  e  f  g  h  i  j   tuple x    5 for x in range 10

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Sounds like you re approaching your problem the wrong way to me   Rewrite your code to use a tuple or write a class to store all of the data

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In your case  I would use YAML    That is an elegant and professional standard for dealing with multiple parameters  The values are loaded from a separate file  You can see some info in this link     https   keleshev com yaml-quick-introduction  But it is easier to Google it  as it is a standard  there are hundreds of info about it  you can find what best fits to your understanding      Best regards

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What s the problem   in fact     If you really need or want 10 a  b  c  d  e  f  g  h  i  j   there will be no other possibility  at a time or another  to write a and write b and write c       If the values are all different  you will be obliged to write for exemple  a   12 b   sun  c   A     where A is a class  d   range 1 102 5  e    line in filehandler if line rstrip    f   0 12358 g   True h   random choice i   re compile        ab     lt span gt    j    78 89 90 0    that is to say defining the  variables  individually   Or   using another writing  no need to use      a b c d e f g h i j    12  sun  A   range 1 102 5     line for line in filehandler if line rstrip      0 12358 True random choice   re compile        ab     lt span gt     78 89 90 0    or  a b c d e f g h i j     12  sun  A   range 1 102 5     line for line in filehandler if line rstrip      0 12358 True random choice   re compile        ab     lt span gt     78 89 90 0        If some of them must have the same value  is the problem that it s too long to write   a  b  c  d  e  f  g  h  i  j   True  True  True  True  True  False  True  True   True  True       Then you can write   a b c d e g h i k j True f   False      I don t understand what is exactly your problem  If you want to write a code  you re obliged to use the characters required by the writing of the instructions and definitions   What else     I wonder if your question isn t the sign that you misunderstand something   When one writes a   10   one don t create a variable in the sense of  chunk of memory whose value can change   This instruction    either triggers the creation of an object of type integer and value 10 and the binding of a name  a  with this object in the current namespace  or re-assign the name  a  in the namespace to the object 10  because  a  was precedently binded to another object    I say that because I don t see the utility to define 10 identifiers a b c    pointing to False or True  If these values don t change during the execution  why 10 identifiers   And if they change  why defining the identifiers first    they will be created when needed if not priorly defined  Your question appears weird to me

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Use a list dictionary or define your own class to encapsulate the stuff you re defining  but if you need all those variables you can do   a   b   c   d   e   g   h   i   j   True f   False

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a  b  c  d  e  g  h  i  j    True   9 f   False

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When people are suggesting  use a list or tuple or other data structure   what they re saying is that  when you have a lot of different values that you care about  naming them all separately as local variables may not be the best way to do things   Instead  you may want to gather them together into a larger data structure that can be stored in a single local variable   intuited showed how you might use a dictionary for this  and Chris Lutz showed how to use a tuple for temporary storage before unpacking into separate variables  but another option to consider is to use collections namedtuple to bundle the values more permanently   So you might do something like     Define the attributes of our named tuple from collections import namedtuple DataHolder   namedtuple  DataHolder    a b c d e f g      Store our data data   DataHolder True  True  True  True  True  False  True     Retrieve our data print data  print data a  data f    Real code would hopefully use more meaningful names than  DataHolder  and the letters of the alphabet  of course

[python] More elegant way of declaring multiple variables at the same time

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