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Python float formatting

Jul 8, 2022

References:

• https://stackoverflow.com/questions/45310254/fixed-digits-after-decimal-with-f-strings
• https://docs.python.org/3/library/string.html#format-string-syntax
• https://peps.python.org/pep-0498/#format-specifiers
• https://cheatography.com/brianallan/cheat-sheets/python-f-strings-number-formatting/
• https://appdividend.com/2022/06/23/how-to-format-float-values-in-python/

Key notes:

• use Format specifiers to format float numbers

  f'{value:{width}.{precision}}'

• examples:
• use %

  x = 1234.5678
  print("%.3f" % x)
  

   179.496
  

• use f

  x = 1e6 + 0.12345
  

  • add comma to large numbers

    print(f'{x:,.6f}')  #display 6 digits after the decimal point
    print(f'{x:,.3f}')  #display 3 digits after the decimal point
    

     1,000,000.123450
     1,000,000.123
    

  • no comma for large numbers

    print(f'{x:.6f}')  #display 6 digits after the decimal point
    

     1000000.123450
    

  • pad (i.e. fixed width)

    print(f'{x:20,.3f}') 
    

         1,000,000.123
    

Python float format: Complete Table

The basic packages for data processing, mathematical and scitific calculations.

Number	Format	Output	Description
3.1415926	{:.2f}	3.14	Format float 2 decimal places
3.1415926	{:+.2f}	+3.14	Format float 2 decimal places with sign
-1	{:+.2f}	-1.00	Format float 2 decimal places with sign
2.71828	{:.0f}	3	Format float with no decimal places
4	{:0>2d}	04	Pad number with zeros (left padding, width 2)
4	{:x<4d}	4xxx	Pad number with x's (right padding, width 4)
10	{:x<4d}	10xx	Pad number with x's (right padding, width 4)
1000000	{:,}	1,000,000	Number format with comma separator
0.35	{:.2%}	35.00%	Format percentage
1000000000	{:.2e}	1.00e+09	Exponent notation
11	{:11d}	11	Right aligned (default, width 10)
11	{:<11d}	11	Left aligned (width 10)
11	{:^11d}	11	Center aligned (width 10)