How to get a random number in Ruby

Question

How do I generate a random number between 0 and n

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Maybe it help you  I use this in my app  https   github com rubyworks facets class String      Create a random String of given length  using given character set         Character set is an Array which can contain Ranges  Arrays  Characters         Examples             String random           gt   D9DxFIaqR3dr8Ct1AfmFxHxqGsmA4Oz3              String random 10            gt   t8BIna341S              String random 10    a    z              gt   nstpvixfri              String random 10    0    9               gt   0982541042              String random 10    0    9   A    F               gt   3EBF48AD3D              BASE64 CHAR SET      A    Z    a    z    0    9         -           String random 10  BASE64 CHAR SET            gt   xM 1t3qcNn              SPECIAL CHARS                                    amp                    -                                                                                     lt      gt            BASE91 CHAR SET      A    Z    a    z    0    9   SPECIAL CHARS          String random 10  BASE91 CHAR SET             gt   S Z z J v           CREDIT  Tilo Sloboda         SEE  https   gist github com tilo 3ee8d94871d30416feba         TODO  Move to random rb in standard library     def self random len 32  character set     A    Z    a    z    0    9        chars   character set map  x  x is a  Range    x to a   x   flatten     Array new len   chars sample   join   end  end   https   github com rubyworks facets blob 5569b03b4c6fd25897444a266ffe25872284be2b lib core facets string random rb  It works fine for me

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Well  I figured it out  Apparently there is a builtin     function called rand   rand n   1    If someone answers with a more detailed answer  I ll mark that as the correct answer

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If you re not only seeking for a number but also hex or uuid it s worth mentioning that the SecureRandom module found its way from ActiveSupport to the ruby core in 1 9 2   So without the need for a full blown framework   require  securerandom   p SecureRandom random number 100     gt  15 p SecureRandom random number 100     gt  88  p SecureRandom random number    gt  0 596506046187744 p SecureRandom random number    gt  0 350621695741409  p SecureRandom hex    gt   eb693ec8252cd630102fd0d0fb7c3485    It s documented here  Ruby 1 9 3 - Module  SecureRandom  lib securerandom rb

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This link is going to be helpful regarding this   http   ruby-doc org core-1 9 3 Random html  And some more clarity below over the random numbers in ruby   Generate an integer from 0 to 10  puts  rand     10  to i   Generate a number from 0 to 10 In a more readable way  puts rand 10    Generate a number from 10 to 15 Including 15  puts rand 10  15    Non-Random Random Numbers  Generate the same sequence of numbers every time the program is run  srand 5    Generate 10 random numbers  puts  0  10  map rand 0  10

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What about this   n   3  0  n  to a sample

User · Answer

You can simply use random number   If a positive integer is given as n  random number returns an integer  0  lt   random number  lt  n   Use it like this   any number   SecureRandom random number 100     The output will be any number between 0 and 100

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rand 6        gt  gives a random number between 0 and 6 inclusively  rand 1  6     gt  gives a random number between 1 and 6 inclusively   Note that the range option is only available in newer 1 9  I believe  versions of ruby

User · Answer

Use rand range   From Ruby Random Numbers      If you needed a random integer to simulate a roll of a six-sided die  you d use  1   rand 6   A roll in craps could be simulated with 2   rand 6    rand 6        Finally  if you just need a random float  just call rand with no arguments      As Marc-Andr   Lafortune mentions in his answer below  go upvote it   Ruby 1 9 2 has its own Random class  that Marc-Andr   himself helped to debug  hence the 1 9 2 target for that feature    For instance  in this game where you need to guess 10 numbers  you can initialize them with   10 times map  20   Random rand 11        gt   26  26  22  20  30  26  23  23  25  22    Note     Using Random new rand 20  30   using Random new  generally would not be a good idea  as explained in detail  again  by Marc-Andr   Lafortune  in his answer  again   But if you don t use Random new  then the class method rand only takes a max value  not a Range  as banister  energetically  points out in the comment  and as documented in the docs for Random    Only the instance method can take a Range  as illustrated by generate a random number with 7 digits    This is why the equivalent of Random new rand 20  30  would be 20   Random rand 11   since Random rand int  returns    a random integer greater than or equal to zero and less than the argument     20  30 includes 30  I need to come up with a random number between 0 and 11  excluding 11

User · Answer

Easy way to get random number in ruby is   def random        1  10  to a sample to s end

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you can do rand range   x   rand 1  5

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Simplest answer to the question   rand 0  n

User · Answer

Well  I figured it out  Apparently there is a builtin     function called rand   rand n   1    If someone answers with a more detailed answer  I ll mark that as the correct answer

User · Answer

Well  I figured it out  Apparently there is a builtin     function called rand   rand n   1    If someone answers with a more detailed answer  I ll mark that as the correct answer

User · Answer

You can generate a random number with the rand method  The argument passed to the rand method should be an integer or a range  and returns a corresponding random number within the range   rand 9          this generates a number between 0 to 8 rand 0    9     this generates a number between 0 to 9 rand 1    50    this generates a number between 1 to 50  rand m    n    m is the start of the number range  n is the end of number range

User · Answer

Well  I figured it out  Apparently there is a builtin     function called rand   rand n   1    If someone answers with a more detailed answer  I ll mark that as the correct answer

User · Answer

range   10  50  rand range   or  range to a sample  or  range to a shuffle this will shuffle whole array and you can pick a random number by first or last or any from this array to pick random one

User · Answer

If you re not only seeking for a number but also hex or uuid it s worth mentioning that the SecureRandom module found its way from ActiveSupport to the ruby core in 1 9 2   So without the need for a full blown framework   require  securerandom   p SecureRandom random number 100     gt  15 p SecureRandom random number 100     gt  88  p SecureRandom random number    gt  0 596506046187744 p SecureRandom random number    gt  0 350621695741409  p SecureRandom hex    gt   eb693ec8252cd630102fd0d0fb7c3485    It s documented here  Ruby 1 9 3 - Module  SecureRandom  lib securerandom rb

User · Answer

Simplest answer to the question   rand 0  n

User · Answer

Use rand range   From Ruby Random Numbers      If you needed a random integer to simulate a roll of a six-sided die  you d use  1   rand 6   A roll in craps could be simulated with 2   rand 6    rand 6        Finally  if you just need a random float  just call rand with no arguments      As Marc-Andr   Lafortune mentions in his answer below  go upvote it   Ruby 1 9 2 has its own Random class  that Marc-Andr   himself helped to debug  hence the 1 9 2 target for that feature    For instance  in this game where you need to guess 10 numbers  you can initialize them with   10 times map  20   Random rand 11        gt   26  26  22  20  30  26  23  23  25  22    Note     Using Random new rand 20  30   using Random new  generally would not be a good idea  as explained in detail  again  by Marc-Andr   Lafortune  in his answer  again   But if you don t use Random new  then the class method rand only takes a max value  not a Range  as banister  energetically  points out in the comment  and as documented in the docs for Random    Only the instance method can take a Range  as illustrated by generate a random number with 7 digits    This is why the equivalent of Random new rand 20  30  would be 20   Random rand 11   since Random rand int  returns    a random integer greater than or equal to zero and less than the argument     20  30 includes 30  I need to come up with a random number between 0 and 11  excluding 11

User · Answer

you can do rand range   x   rand 1  5

User · Answer

You can generate a random number with the rand method  The argument passed to the rand method should be an integer or a range  and returns a corresponding random number within the range   rand 9          this generates a number between 0 to 8 rand 0    9     this generates a number between 0 to 9 rand 1    50    this generates a number between 1 to 50  rand m    n    m is the start of the number range  n is the end of number range

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Don t forget to seed the RNG with srand   first

User · Answer

While you can use rand 42-10    10 to get a random number between 10 and 42  where 10 is inclusive and 42 exclusive   there s a better way since Ruby 1 9 3  where you are able to call   rand 10   42      gt  13   Available for all versions of Ruby by requiring my backports gem   Ruby 1 9 2 also introduced the Random class so you can create your own random number generator objects and has a nice API   r   Random new r rand 10   42      gt  22 r bytes 3      gt   rnd    The Random class itself acts as a random generator  so you call directly   Random rand 10   42      gt  same as rand 10   42    Notes on Random new  In most cases  the simplest is to use rand or Random rand  Creating a new random generator each time you want a random number is a really bad idea  If you do this  you will get the random properties of the initial seeding algorithm which are atrocious compared to the properties of the random generator itself   If you use Random new  you should thus call it as rarely as possible  for example once as MyApp  Random   Random new and use it everywhere else   The cases where Random new is helpful are the following    you are writing a gem and don t want to interfere with the sequence of rand Random rand that the main programs might be relying on you want separate reproducible sequences of random numbers  say one per thread  you want to be able to save and resume a reproducible sequence of random numbers  easy as Random objects can marshalled

User · Answer

rand 6        gt  gives a random number between 0 and 6 inclusively  rand 1  6     gt  gives a random number between 1 and 6 inclusively   Note that the range option is only available in newer 1 9  I believe  versions of ruby

User · Answer

Use rand range   From Ruby Random Numbers      If you needed a random integer to simulate a roll of a six-sided die  you d use  1   rand 6   A roll in craps could be simulated with 2   rand 6    rand 6        Finally  if you just need a random float  just call rand with no arguments      As Marc-Andr   Lafortune mentions in his answer below  go upvote it   Ruby 1 9 2 has its own Random class  that Marc-Andr   himself helped to debug  hence the 1 9 2 target for that feature    For instance  in this game where you need to guess 10 numbers  you can initialize them with   10 times map  20   Random rand 11        gt   26  26  22  20  30  26  23  23  25  22    Note     Using Random new rand 20  30   using Random new  generally would not be a good idea  as explained in detail  again  by Marc-Andr   Lafortune  in his answer  again   But if you don t use Random new  then the class method rand only takes a max value  not a Range  as banister  energetically  points out in the comment  and as documented in the docs for Random    Only the instance method can take a Range  as illustrated by generate a random number with 7 digits    This is why the equivalent of Random new rand 20  30  would be 20   Random rand 11   since Random rand int  returns    a random integer greater than or equal to zero and less than the argument     20  30 includes 30  I need to come up with a random number between 0 and 11  excluding 11

User · Answer

Easy way to get random number in ruby is   def random        1  10  to a sample to s end

User · Answer

Try array shuffle method for randomization  array    1  10  to a array shuffle first

User · Answer

How about this one   num   Random new num rand 1  n

User · Answer

Try array shuffle method for randomization  array    1  10  to a array shuffle first

User · Answer

Don t forget to seed the RNG with srand   first

User · Answer

Maybe it help you  I use this in my app  https   github com rubyworks facets class String      Create a random String of given length  using given character set         Character set is an Array which can contain Ranges  Arrays  Characters         Examples             String random           gt   D9DxFIaqR3dr8Ct1AfmFxHxqGsmA4Oz3              String random 10            gt   t8BIna341S              String random 10    a    z              gt   nstpvixfri              String random 10    0    9               gt   0982541042              String random 10    0    9   A    F               gt   3EBF48AD3D              BASE64 CHAR SET      A    Z    a    z    0    9         -           String random 10  BASE64 CHAR SET            gt   xM 1t3qcNn              SPECIAL CHARS                                    amp                    -                                                                                     lt      gt            BASE91 CHAR SET      A    Z    a    z    0    9   SPECIAL CHARS          String random 10  BASE91 CHAR SET             gt   S Z z J v           CREDIT  Tilo Sloboda         SEE  https   gist github com tilo 3ee8d94871d30416feba         TODO  Move to random rb in standard library     def self random len 32  character set     A    Z    a    z    0    9        chars   character set map  x  x is a  Range    x to a   x   flatten     Array new len   chars sample   join   end  end   https   github com rubyworks facets blob 5569b03b4c6fd25897444a266ffe25872284be2b lib core facets string random rb  It works fine for me

User · Answer

Use rand range   From Ruby Random Numbers      If you needed a random integer to simulate a roll of a six-sided die  you d use  1   rand 6   A roll in craps could be simulated with 2   rand 6    rand 6        Finally  if you just need a random float  just call rand with no arguments      As Marc-Andr   Lafortune mentions in his answer below  go upvote it   Ruby 1 9 2 has its own Random class  that Marc-Andr   himself helped to debug  hence the 1 9 2 target for that feature    For instance  in this game where you need to guess 10 numbers  you can initialize them with   10 times map  20   Random rand 11        gt   26  26  22  20  30  26  23  23  25  22    Note     Using Random new rand 20  30   using Random new  generally would not be a good idea  as explained in detail  again  by Marc-Andr   Lafortune  in his answer  again   But if you don t use Random new  then the class method rand only takes a max value  not a Range  as banister  energetically  points out in the comment  and as documented in the docs for Random    Only the instance method can take a Range  as illustrated by generate a random number with 7 digits    This is why the equivalent of Random new rand 20  30  would be 20   Random rand 11   since Random rand int  returns    a random integer greater than or equal to zero and less than the argument     20  30 includes 30  I need to come up with a random number between 0 and 11  excluding 11

User · Answer

Don t forget to seed the RNG with srand   first

User · Answer

You can simply use random number   If a positive integer is given as n  random number returns an integer  0  lt   random number  lt  n   Use it like this   any number   SecureRandom random number 100     The output will be any number between 0 and 100

User · Answer

What about this   n   3  0  n  to a sample

User · Answer

This link is going to be helpful regarding this   http   ruby-doc org core-1 9 3 Random html  And some more clarity below over the random numbers in ruby   Generate an integer from 0 to 10  puts  rand     10  to i   Generate a number from 0 to 10 In a more readable way  puts rand 10    Generate a number from 10 to 15 Including 15  puts rand 10  15    Non-Random Random Numbers  Generate the same sequence of numbers every time the program is run  srand 5    Generate 10 random numbers  puts  0  10  map rand 0  10

User · Answer

While you can use rand 42-10    10 to get a random number between 10 and 42  where 10 is inclusive and 42 exclusive   there s a better way since Ruby 1 9 3  where you are able to call   rand 10   42      gt  13   Available for all versions of Ruby by requiring my backports gem   Ruby 1 9 2 also introduced the Random class so you can create your own random number generator objects and has a nice API   r   Random new r rand 10   42      gt  22 r bytes 3      gt   rnd    The Random class itself acts as a random generator  so you call directly   Random rand 10   42      gt  same as rand 10   42    Notes on Random new  In most cases  the simplest is to use rand or Random rand  Creating a new random generator each time you want a random number is a really bad idea  If you do this  you will get the random properties of the initial seeding algorithm which are atrocious compared to the properties of the random generator itself   If you use Random new  you should thus call it as rarely as possible  for example once as MyApp  Random   Random new and use it everywhere else   The cases where Random new is helpful are the following    you are writing a gem and don t want to interfere with the sequence of rand Random rand that the main programs might be relying on you want separate reproducible sequences of random numbers  say one per thread  you want to be able to save and resume a reproducible sequence of random numbers  easy as Random objects can marshalled

User · Answer

Don t forget to seed the RNG with srand   first

User · Answer

How about this one   num   Random new num rand 1  n

User · Answer

range   10  50  rand range   or  range to a sample  or  range to a shuffle this will shuffle whole array and you can pick a random number by first or last or any from this array to pick random one

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