Understanding the print format %.3 in python

Question

Can someone help me with the explanation of what the "'f %" meaning in the following code?

print('Slope: %.3f' % lr.w_[1])

Answer 1

Here is a list of string formatting options in Python. You use a % as a placeholder, which is replaced by lr.w_[1] in this case. The f then refers to "Floating point decimal format". The .3 indicates to round to 3 places after the decimal point.

Answer 2

It prints a decimal number, with 3 decimal digit accuracy.

In [1]: print('Slope: %.3f' % 1.123)
Slope: 1.123

In [2]: print('Slope: %.3f' % 1.12345)
Slope: 1.123

In [3]: print('Slope: %.3f' % 1.1)
Slope: 1.100

In [4]: print('Slope: %.3f' % 1.1237)
Slope: 1.124

As you can see by the 4th example is rounds by standard rounding rules

Answer 3

%.3f

f: Floating point, which means that the value that is going to be printed is a real number.

.3 is for the number of decimals after the point. That means that the real value to be printed will have 3 digits after the point.

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For example:

print('%.3f' % 3.14159)          # Prints 3.142
print('%.2f' % 3.141592653589)   # Prints 3.14