Truncate to three decimals in Python

Question

How do I get 1324343032 324   As you can see below  the following do not work    gt  gt 1324343032 324325235   1000   1000 1324343032 3243253  gt  gt int 1324343032 324325235   1000    1000 0 1324343032 3239999  gt  gt round int 1324343032 324325235   1000    1000 0 3  1324343032 3239999  gt  gt str 1324343032 3239999   1324343032 32

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Function def truncate number  float  digits  int  - gt  float      pow10   10    digits     return number   pow10    1   pow10  Test code f1   1 2666666 f2   truncate f1  3  print f1  f2   Output 1 2666666 1 266  Explain It shifts f1 numbers digits times to the left  then cuts all decimals and finally shifts back the numbers digits times to the right  Example in a sequence  1 2666666   number 1266 6666   number   pow10 1266 0      number   pow10    1 1 266       number   pow10    1   pow10

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3f   1324343032 324325235    It s OK just in this particular case   Simply change the number a little bit   1324343032 324725235  And then      3f   1324343032 324725235    gives you 1324343032 325  Try this instead   def trun n d n d       s repr n  split          if  len s   1           return int s 0       return float s 0      s 1   d     Another option for trun n d   def trun n d n d       dp   repr n  find       dot position     if dp    -1            return int n       return float repr n   dp d 1     Yet another option   a oneliner one  for trun n d  this  assumes  n  is a str and  d  is an int    def trun n d n d       return    n if not n find      1 else n  n find      d 1       trun n d gives you the desired output in both  Python 2 7 and Python 3 6  trun n d 1324343032 324325235 3  returns 1324343032 324  Likewise  trun n d 1324343032 324725235 3  returns 1324343032 324    Note 1 In Python 3 6  and  probably  in Python 3 x  something like this  works just fine   def trun n d n d       return int n 10  d  10  d   But  this way  the rounding ghost is always lurking around   Note 2 In situations like this  due to python s number internals  like rounding and lack of precision  working with n as a str is way much better than using its int counterpart  you can always cast your number to a float at the end

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Maybe this way   def myTrunc theNumber  theDigits        myDigits   10    theDigits     return  int theNumber   myDigits    myDigits

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I am trying to generate a random number between 5 to 7 and want to limit it to 3 decimal places   import random  num   float    3f    random uniform 5  7   print  num

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After looking for a way to solve this problem  without loading any Python 3 module or extra mathematical operations  I solved the problem using only str format   e  float    I think this way is faster than using other mathematical operations  like in the most commom solution  I needed a fast solution because I work with a very very large dataset and so for its working very well here    def truncate number f number  n decimals         strFormNum     0      str n decimals 5     f         trunc num   float strFormNum format f number   -5         return trunc num     Testing the  trunc num    function test num   1150 252   idx  truncate number test num  idx   for idx in range 0  20     It returns the following output      0  4 0     1  4 5     2  4 56     3  4 563     4  4 5634     5  4 56349     6  4 563492     7  4 563492     8  4 56349206     9  4 563492063     10  4 5634920634     11  4 56349206349     12  4 563492063492     13  4 563492063492     14  4 56349206349206     15  4 563492063492063     16  4 563492063492063     17  4 563492063492063     18  4 563492063492063     19  4 563492063492063

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gt  gt  gt  float 1324343032 324325235    float 1000    float 1000   1324343032 3243253   gt  gt  gt  round float 1324343032 324325235    float 1000    float 1000   3   1324343032 324

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I believe using the format function is a bad idea  Please see the below  It rounds the value  I use Python 3 6    gt  gt  gt     3f   1 9999999   2 000    Use a regular expression instead    gt  gt  gt  re match r  d   d 3    str 1 999999   group 0   1 999

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Maybe python changed since this question  all of the below seem to work well  Python2 7  int 1324343032 324325235   1000    1000 0 float int 1324343032 324325235   1000     1000 round int 1324343032 324325235   1000    1000 0 3    result for all of the above is 1324343032 324

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You can also use   import math  nValeur   format float input  Quelle valeur             3f     In Python 3 6 it would work

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Almo s link explains why this happens  To solve the problem  use the decimal library

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I suggest next solution   def my floor num  precision      return f  num   precision 1 f    -1   my floor 1 026456 2    1 02

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I think the best and proper way is to use decimal module   import decimal  a   1324343032 324325235  decimal val   decimal Decimal str a   quantize     decimal Decimal   001        rounding decimal ROUND DOWN   float val   float decimal val   print decimal val   gt  gt  gt 1324343032 324  print float val   gt  gt  gt 1324343032 324   You can use different values for rounding decimal ROUND DOWN  available options are ROUND CEILING  ROUND DOWN  ROUND FLOOR  ROUND HALF DOWN  ROUND HALF EVEN  ROUND HALF UP  ROUND UP  and ROUND 05UP  You can find explanation of each option here in docs

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You can use an additional float   around it if you want to preserve it as a float    3f   1324343032 324325235

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a   1 0123456789 dec   3   keep this many decimals p   10   raise 10 to this power a   10    p    10     p - dec    10    dec  gt  gt  gt  1 012

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Use the decimal module  But if you must use floats and still somehow coerce them into a given number of decimal points converting to string an back provides a  rather clumsy  I m afraid  method of doing it    gt  gt  gt  q   1324343032 324325235   1000   1000  gt  gt  gt  a      3f    q  gt  gt  gt  a  1324343032 324   gt  gt  gt  b   float a   gt  gt  gt  b 1324343032 324   So   float   3 f    q

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You can use the following function to truncate a number to a set number of decimals   import math def truncate number  digits  - gt  float      stepper   10 0    digits     return math trunc stepper   number    stepper   Usage    gt  gt  gt  truncate 1324343032 324325235  3  1324343032 324

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Okay  this is just another approach to solve this working on the number as a string and performing a simple slice of it  This gives you a truncated output of the number instead of a rounded one  num   str 1324343032 324325235  i   num index  quot   quot   truncated   num  i   4       print truncated   Output   1324343032 324   Of course then you can parse  float truncated

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I develop a good solution  I know there is much If statements  but It works   Its only for  lt 1 numbers  def truncate number  digits  - gt  float      startCounting   False     if number  lt  1        number str   str     20f   format number         resp            count digits   0       for i in range 0  len number str            if number str i      0  and number str i         and number str i                    startCounting   True         if startCounting            count digits   count digits   1         resp   resp   number str i          if count digits    digits              break       return resp     else        return number

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How about this   In  1      3f    round 1324343032 324325235   1000   1000 3  Out 1    1324343032 324    Possible duplicate of round   in Python doesn  39 t seem to be rounding properly   EDIT    Given the additional comments I believe you ll want to do   In   Decimal    3f     1324343032 324325235   1000   1000   Out  Decimal  1324343032 324     The floating point accuracy isn t going to be what you want   In   3 324 Out  3 3239999999999998    all examples are with Python 2 6 5

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I ve found another solution  it must be more efficient than  string witchcraft  workarounds     gt  gt  gt  import decimal   By default rounding setting in python is decimal ROUND HALF EVEN  gt  gt  gt  decimal getcontext   rounding   decimal ROUND DOWN  gt  gt  gt  c   decimal Decimal 34 1499123    By default it should return 34 15 due to  99  after  34 14   gt  gt  gt  round c 2  Decimal  34 14    gt  gt  gt  float round c 2   34 14  gt  gt  gt  print round c 2   34 14   About decimals module  About rounding settings

[python] Truncate to three decimals in Python

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