Understanding the print format %.3 in python

python 3 print format
python print example
python 3 print variable
python print float precision
python format
python format string padding
python print variable
python number format

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

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

Python Tutorial: Formatted Output, formatted output in three ways: the string methods ljust, rjust, center, format or Unfortunately, string modulo "%" is still available in Python3 and what is even  Python 3 This is a tutorial in Python3, but this chapter of our course is available in a version for Python 2.x as well: Formatted Output in Python 2.x. Classroom Training Courses The goal of this website is to provide educational material, allowing you to learn Python on your own.

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

Your Guide to the Python print() Function – Real Python, Print Is a Function in Python 3; print Was a Statement in Python 2 deepen your understanding: The Python print() Function: Go Beyond the Basics You can use it to display formatted messages onto the screen and perhaps  Python has had awesome string formatters for many years but the documentation on them is far too theoretic and technical. With this site we try to show you the most common use-cases covered by the old and new style string formatting API with practical examples. All examples on this page work out of the box with with Python 2.7, 3.2, 3.3, 3.4

%.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.


For example:

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

7. Input and Output, 7.1.3. Manual String Formatting¶. Here's the same table of squares and cubes, formatted manually: >>> Understanding Python print() You know how to use print() quite well at this point, but knowing what it is will allow you to use it even more effectively and consciously. After reading this section, you’ll understand how printing in Python has improved over the years. Print Is a Function in Python 3. You’ve seen that print() is a function in

7. Input and Output, There are two ways to format your output; the first way is to do all the for x in range(1, 11): print(repr(x).rjust(2), repr(x*x).rjust(3), end=' ') . Our team prefers to use format instead of str.format in every case, and while trying to learn how to use format() in Python I encountered something which I have no idea of why it happened, and this is the problem: 3.30 What will be displayed by the following code? (note ? represents a blank space)

Python, String modulo operator ( % ) is still available in Python(3.x) and user is using it widely. But nowadays the old style of formatting is removed from the language. The format () method was added in Python (2.6). Format method of strings requires more manual effort. User use {} to mark where a variable will be substituted and can provide detailed formatting directives, but user also needs to provide the information to be formatted. This method lets us concatenate elements within an output through

String Formatting with str.format() in Python 3, Understanding Class and Instance Variables in Python 3 Python's str.format() method of the string class allows you to do variable  Python’s str.format () method of the string class allows you to do variable substitutions and value formatting. This lets you concatenate elements together within a string through positional formatting. This tutorial will guide you through some of the common uses of formatters in Python, which can help make your code and program more readable

Comments
  • Just a comment: This is old string notation. Have a look at str.format() instead.
  • @Anton vBR building off of that, here is OPs code converted to use .format : print('Slope: {.3f}'.format(lr.w_[1])
  • "f" stands for floating point. The integer (here 3) represents the number of decimals after the point. "%.3f" will print a real number with 3 figures after the point.
  • @Kefeng91 I missed that this was in question too. Thank you very much, answer updated!