How to format a floating number to fixed width in Python

Question:

How do I format a floating number to a fixed width with the following requirements:

  1. Leading zero if n < 1
  2. Add trailing decimal zero(s) to fill up fixed width
  3. Truncate decimal digits past fixed width
  4. Align all decimal points

For example:

% formatter something like '{:06}'
numbers = [23.23, 0.123334987, 1, 4.223, 9887.2]

for number in numbers:
    print formatter.format(number)

The output would be like

  23.2300
   0.1233
   1.0000
   4.2230
9887.2000
Asked By: hobbes3

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Source

Answers:

numbers = [23.23, 0.1233, 1.0, 4.223, 9887.2]                                                                                                                                                   
                                                                                                                                                                                                
for x in numbers:                                                                                                                                                                               
    print("{:10.4f}".format(x))

prints

   23.2300
    0.1233
    1.0000
    4.2230
 9887.2000

The format specifier inside the curly braces follows the Python format string syntax. Specifically, in this case, it consists of the following parts:

  • The empty string before the colon means "take the next provided argument to format()" – in this case the x as the only argument.
  • The 10.4f part after the colon is the format specification.
  • The f denotes fixed-point notation.
  • The 10 is the total width of the field being printed, lefted-padded by spaces.
  • The 4 is the number of digits after the decimal point.
Answered By: Sven Marnach

In python3 the following works:

>>> v=10.4
>>> print('% 6.2f' % v)
  10.40
>>> print('% 12.1f' % v)
        10.4
>>> print('%012.1f' % v)
0000000010.4
Answered By: Scott Roberts

See Python 3.x format string syntax:

IDLE 3.5.1   
numbers = ['23.23', '.1233', '1', '4.223', '9887.2']

for x in numbers:  
    print('{0: >#016.4f}'. format(float(x)))  

     23.2300
      0.1233
      1.0000
      4.2230
   9887.2000
Answered By: readyleader

In Python 3.

GPA = 2.5
print(" %6.1f " % GPA)

6.1f means after the dots 1 digits show if you print 2 digits after the dots you should only %6.2f such that %6.3f 3 digits print after the point.

Answered By: Usman Zia

It has been a few years since this was answered, but as of Python 3.6 (PEP498) you could use the new f-strings:

numbers = [23.23, 0.123334987, 1, 4.223, 9887.2]

for number in numbers:
    print(f'{number:9.4f}')

Prints:

  23.2300
   0.1233
   1.0000
   4.2230
9887.2000
Answered By: artomason

You can also left pad with zeros. For example if you want number to have 9 characters length, left padded with zeros use:

print('{:09.3f}'.format(number))

Thus, if number = 4.656, the output is: 00004.656

For your example the output will look like this:

numbers  = [23.2300, 0.1233, 1.0000, 4.2230, 9887.2000]
for x in numbers: 
    print('{:010.4f}'.format(x))

prints:

00023.2300
00000.1233
00001.0000
00004.2230
09887.2000

One example where this may be useful is when you want to properly list filenames in alphabetical order. I noticed in some linux systems, the number is: 1,10,11,..2,20,21,…

Thus if you want to enforce the necessary numeric order in filenames, you need to left pad with the appropriate number of zeros.

Answered By: elcymon

I needed something similar for arrays. That helped me

some_array_rounded=np.around(some_array, 5)
Answered By: Anton

This will print 76.66:

print("Number: ", f"{76.663254: .2f}")
Answered By: Matt

I tried all the options like

  1. pd.options.display.float_format = '{:.4f}'.format
  2. pd.set_option('display.float_format', str)
  3. pd.set_option('display.float_format', lambda x: f'%.{len(str(x%1))-2}f' % x)
  4. pd.set_option('display.float_format', lambda x: '%.3f' % x)

but nothing worked for me.

so while assigning the variable/value (var1) to a variable (say num1) I used round(val,5) like

num1 = round(var1,5)

This is a crude method as you have to use this round function in each assignment. But this ensures you control on how it happens and get what you want.

Answered By: Shekhar Mahajan

Using f-string literals:

>>> number = 12.34
>>> print(f"{number}")
12.34
>>> print(f"{number:10f}")
 12.340000
>>> print(f"{number:10.4f}")
   12.3400

The 10.4f after the colon : is the format specification, with 10 being the width in characters of the whole number (including spaces), and the second number 4 being the number of decimal places, and the f standing for floating-point number.

It’s also possible to use variables instead of hard-coding the width and the number of decimal places:

>>> number = 12.34
>>> width = 10
>>> decimals = 4
>>> print(f"{number:{width}.{decimals}f}")
   12.3400
Answered By: Flimm