How to Print a Float Without Scientific Notation in Python?

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Problem Formulation

If you print a float value in Python that is smaller than 0.0001, Python will use the scientific notation for small numbers such as 1e-05 that is short for 1*1/10**-5.

Here’s an example output when printing smaller and smaller floats to the shell. If there are more than three zeros after the decimal point, Python will use the scientific notation:

>>> print(0.01)
>>> print(0.001)
>>> print(0.0001)
>>> print(0.00001)
>>> print(0.000001)

Problem: How to display the numbers non-scientifically?

Here’s your desired output:

>>> print(0.00001)

Solution 1: f-String Formatting

The most powerful way is to use Python’s capabilities for string formatting with f-strings, i.e., special types of formatting string that are enclosed in f'...'. Within a given f-string, you can use the {...:f} format specifier to tell Python to use floating point notation for the number preceding the :f suffix. Thus, to print the number my_float = 0.00001 non-scientifically, use the expression print(f'{my_float:f}').

my_float = 0.00001
# 0.000010

The problem with this approach is that if you try it for smaller numbers, it only display '0' digits because the default precision is constant:

my_float = 0.0000001
# 0.000000

The default :f precision generates a string with nine characters (including floating point). If the float value cannot be represented within nine characters, the string representation of the float will be cut off. This is clearly not what you want!

Solution 2: f-String Formatting with Precision

The best way to print even small float numbers is to use f-strings, i.e., special types of formatting string that are enclosed in f'...'. Within a given f-string, you can use the {...:.12f} format specifier to tell Python to use floating point precision with 12 digits after the decimal point. Thus, to print the number my_float = 0.0000001 non-scientifically with 14 decimal digits, use the expression print(f'{my_float:.14f}').

my_float = 0.00001
# 0.00001000000000

And with 8 digits:

my_float = 0.00001
# 0.00001000

Feel free to watch my short video tutorial on f-strings and the alternative string.format() function here:

Python format() Function: No-BS Guide by Example

However, if you want to automatically suppress trailing '0' digits, this method won’t help:

Solution 3: NumPy format_float_positional()

The np.format_float_positional() method formats a given float as a decimal string using the non-scientific positional notation. The first argument is the float to be displayed. The optional trim argument when set to '-' trims trailing zeros and any trailing decimal point if not needed.

Here’s a simple example:

import numpy as np

my_float = 0.00001
print(np.format_float_positional(my_float, trim='-'))
# 0.00001

Let’s apply this method to multiple numbers to see that NumPy automatically trims all trailing zeros. For convenience, I’ve defined a simple conversion function using the lambda notation:

>>> pretty_print = lambda x: np.format_float_positional(x, trim='-')
>>> pretty_print(0.001)
>>> pretty_print(0.0001)
>>> pretty_print(0.00001)
>>> pretty_print(0.000001)
>>> pretty_print(0.0000001)
>>> pretty_print(0.00000001)

You can watch the lambda function video introduction here:

Let's Play Finxter - The Lambda Function in Python

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