Fixed digits after decimal with f-strings

When it comes to float numbers, you can use format specifiers:

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

where:

• value is any expression that evaluates to a number
• width specifies the number of characters used in total to display, but if value needs more space than the width specifies then the additional space is used.
• precision indicates the number of characters used after the decimal point

What you are missing is the type specifier for your decimal value. In this link, you an find the available presentation types for floating point and decimal.

Here you have some examples, using the f (Fixed point) presentation type:

# notice that it adds spaces to reach the number of characters specified by width In [1]: f'{1 + 3 * 1.5:10.3f}' Out[1]: ' 5.500' # notice that it uses more characters than the ones specified in width In [2]: f'{3000 + 3 ** (1 / 2):2.1f}' Out[2]: '3001.7' In [3]: f'{1.2345 + 4 ** (1 / 2):9.6f}' Out[3]: ' 3.234500' # omitting width but providing precision will use the required characters to display the number with the the specified decimal places In [4]: f'{1.2345 + 3 * 2:.3f}' Out[4]: '7.234' # not specifying the format will display the number with as many digits as Python calculates In [5]: f'{1.2345 + 3 * 0.5}' Out[5]: '2.7344999999999997' 

Adding to Robᵩ's answer: in case you want to print rather large numbers, using thousand separators can be a great help (note the comma).

>>> f'{a*1000:,.2f}' '10,123.40' 

And in case you want to pad/use a fixed width, the width goes before the comma:

>>> f'{a*1000:20,.2f}' ' 10,123.40' 

Adding to Rob's answer, you can use format specifiers with f strings (more here).

• You can control the number of decimals:

pi = 3.141592653589793238462643383279 print(f'The first 6 decimals of pi are {pi:.6f}.') 

The first 6 decimals of pi are 3.141593. 

• You can convert to percentage:

grade = 29/45 print(f'My grade rounded to 3 decimals is {grade:.3%}.') 

My grade rounded to 3 decimals is 64.444%. 

• You can do other things like print constant length:

from random import randint for i in range(5): print(f'My money is {randint(0, 150):>3}$') 

My money is 126$ My money is 7$ My money is 136$ My money is 15$ My money is 88$ 

• Or even print with a comma thousand separator:

print(f'I am worth {10000000000:,}$') 

I am worth 10,000,000,000$ 

>>> number1 = 10.1234 >>> f'{number1:.2f}' '10.12' 

"{" [field_name] ["!" conversion] [":" format_spec] "}" 

# Let's break it down... # [field_name] => number1 # ["!" conversion] => Not used # [format_spec] => [.precision][type] # => .[2][f] => .2f # where f means Fixed-point notation 

Going further, Format strings have the below syntax. As you can see there is a lot more that can be done.

Syntax: "{" [field_name] ["!" conversion] [":" format_spec] "}" # let's understand what each field means... field_name ::= arg_name ("." attribute_name | "[" element_index "]")* arg_name ::= [identifier | digit+] attribute_name ::= identifier element_index ::= digit+ | index_string index_string ::= <any source character except "]"> + conversion ::= "r" | "s" | "a" format_spec ::= [[fill]align][sign][#][0][width][grouping_option][.precision][type] # Looking at the underlying fields under format_spec... fill ::= <any character> align ::= "<" | ">" | "=" | "^" sign ::= "+" | "-" | " " width ::= digit+ grouping_option ::= "_" | "," precision ::= digit+ type ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%" 

Refer https://docs.python.org/3/library/string.html#format-string-syntax

It seems that no one use dynamic formatter. To use dynamic formatter, use:

WIDTH = 7 PRECISION = 3 TYPE = "f" v = 3 print(f"val = {v:{WIDTH}.{PRECISION}{TYPE}}") 

Other format see: https://docs.python.org/3.6/library/string.html#format-specification-mini-language

Reference: Others SO Answer

Simply

a = 10.1234 print(f"{a:.1f}") 

Output: 10.1

a = 10.1234 print(f"{a:.2f}") 

Output: 10.12

a = 10.1234 print(f"{a:.3f}") 

Output: 10.123

a = 10.1234 print(f"{a:.4f}") 

Output: 10.1234

Just change the value after the decimal point sign which represent how may decimal point you want to print.

a = 10.1234 print(f"{a:0.2f}") 

in 0.2f:

• 0 is telling python to put no limit on the total number of digits to display
• .2 is saying that we want to take only 2 digits after decimal (the result will be same as a round() function)
• f is telling that it's a float number. If you forget f then it will just print 1 less digit after the decimal. In this case, it will be only 1 digit after the decimal.

A detailed video on f-string for numbers https://youtu.be/RtKUsUTY6to?t=606

To make monetary values more readable:

>>> v = 12_093.74 # Currency value with minor currency digits >>> f"{v:,.02f}" '12,093.74' 

See also the Format Specification Mini-Language.

Worth noting that f-strings can be parametrized with double braces. The inner brace is evaluated (firstly) as an expression and it's result (RHS) value is (secondly) inserted into the f-string functionality (as noted in the docs).

i.e. to specify the decimal places as:

for i in range(3): print(f'{1.002:,.{i}f}') > 1 > 1.0 > 1.00 

and

i = ',.5f' print(f'{1.002:{i}}') > 1.00200