Convert floating point number to a certain precision and then copy to string

Question

I have a floating point number  say 135 12345678910  I want to concatenate that value to a string  but only want 135 123456789  With print  I can easily do this by doing something like   print    9f    numvar   with numvar being my original number  Is there an easy way to do this

User · Answer

Python 3 6 Just to make it clear  you can use f-string formatting  This has almost the same syntax as the format method  but make it a bit nicer  Example  print f  numvar  9f     More reading about the new f string   What s new in Python 3 6  same link as above  PEP official documentation Python official documentation Really good blog post - talks about performance too  Here is a diagram of the execution times of the various tested methods  from last link above

User · Answer

It s not print that does the formatting  It s a property of strings  so you can just use  newstring      9f    numvar

User · Answer

In case the precision is not known until runtime  this other formatting option is useful    gt  gt  gt  n   9  gt  gt  gt      f     n  numvar   135 123456789

User · Answer

With Python  lt  3  e g  2 6  see comments  or 2 7   there are two ways to do so     Option one older method string      9f    numvar    Option two newer method string       9f   format numvar    But note that for Python versions above 3  e g  3 2 or 3 3   option two is preferred   For more information on option two  I suggest this link on string formatting from the Python documentation   And for more information on option one  this link will suffice and has info on the various flags   Python 3 6  officially released in December of 2016   added the f string literal  see more information here  which extends the str format method  use of curly braces such that f  numvar  9f   solves the original problem   that is     Option 3  versions 3 6 and higher  newest method string   f  numvar  9f     solves the problem  Check out  Or-Duan s answer for more info  but this method is fast

User · Answer

The str function has a bug  Please try the following  You will see  0 196553  but the right output is  0 196554   Because the str function s default value is ROUND HALF UP    gt  gt  gt  value 0 196553500000   gt  gt  gt  str   f    value  replace

User · Answer

To set precision with 9 digits  get   print    9f    numvar   Return precision with 2 digits   print    2f    numvar    Return precision with 2 digits and float converted value   numvar   4 2345 print float    2f    numvar

User · Answer

Using round    gt  gt  gt  numvar   135 12345678910  gt  gt  gt  str round numvar  9    135 123456789

[python] Convert floating point number to a certain precision, and then copy to string

Python 3.6

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