Formatted Printing in Python

For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))

Python has no "printf" or "sprintf" - use the % operator on a string object which is the format string instead. Let me show you that ...

Firstly, what do we get if we do NOT format?

>>> val = 1. / 17.

>>> print val

0.0588235294118

Here it is, formatted to 4 figures after the decimal place:

>>> val24dp = "%.4f" % val

>>> print val24dp

0.0588

And with a total field width of 8 characters, of which 4 are after the decimal place (the 8 is a total width and NOT the number of places before!)

>>> f2 = "A seventeenth is %8.4f to 4 places" % val

>>> print f2

A seventeenth is   0.0588 to 4 places

Whole numbers are formatted with a "d" - that stands for "decimal" as opposed to "x" for hexadecimal, or the letter "o" for Octal.

>>> n = 5

>>> vv = "There are %3d in stock" % n

>>> print vv

There are   5 in stock

And if I want to format several values at the same time, I can do so by using multiple % based place holders, and then specifying a tuple for formatting.

>>> vx = "There are %d in stock at %.4fp each" % (n,val)

>>> print vx

There are 5 in stock at 0.0588p each

(written 2010-05-25)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

Y108 - Python - String Handling
  [324] The backtick operator in Python and Perl - (2005-05-25)
  [463] Splitting the difference - (2005-10-13)
  [496] Python printf - (2005-11-15)
  [560] The fencepost problem - (2006-01-10)
  [773] Breaking bread - (2006-06-22)
  [903] Pieces of Python - (2006-10-23)
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [954] Splitting Pythons in Bradford - (2006-11-29)
  [970] String duplication - x in Perl, * in Python and Ruby - (2006-12-07)
  [1110] Python - two different splits - (2007-03-15)
  [1195] Regular Express Primer - (2007-05-20)
  [1517] Python - formatting objects - (2008-01-24)
  [1608] Underlining in Perl and Python - the x and * operator in use - (2008-04-12)
  [1876] Python Regular Expressions - (2008-11-08)
  [2284] Strings as collections in Python - (2009-07-12)
  [2406] Pound Sign in Python Program - (2009-09-15)
  [2692] Flexible search and replace in Python - (2010-03-25)
  [2721] Regular Expressions in Python - (2010-04-14)
  [2765] Running operating system commands from your Python program - (2010-05-14)
  [2814] Python - splitting and joining strings - (2010-06-16)
  [3090] Matching to a string - what if it matches in many possible ways? - (2010-12-17)
  [3218] Matching a license plate or product code - Regular Expressions - (2011-03-28)
  [3349] Formatting output in Python through str.format - (2011-07-07)
  [3468] Python string formatting - the move from % to str.format - (2011-10-08)
  [3469] Teaching dilemma - old tricks and techniques, or recent enhancements? - (2011-10-08)
  [3796] Backquote, backtic, str and repr in Python - conversion object to string - (2012-07-05)
  [3886] Formatting output - why we need to, and first Python example - (2012-10-09)
  [4027] Collections in Python - list tuple dict and string. - (2013-03-04)
  [4152] Why are bus fares so high? - (2013-08-18)
  [4213] Formatting options in Python - (2013-11-16)
  [4307] Identifying and clearing denial of service attacks on your Apache server - (2014-09-27)
  [4360] Python - comparison of old and new string formatters - (2014-12-22)
  [4593] Command line parameter handling in Python via the argparse module - (2015-12-08)
  [4595] Python formatting update - including named completions - (2015-12-10)
  [4659] Prining a pound sign from Python AND running from the command line at the same time - (2016-03-03)

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Some other Articles

Course Lunches
The Perl Survey
Tell the Melksham Chamber or you only have yourself to blame
The 500 pound question to get you started
Formatted Printing in Python
The history and future of Melksham Chamber of Commerce
Learning to program in Python 2 ... and / or in Python 3
Blowing our own trumpet
Regional Spatial Strategy and the next 20 years - Whence Wiltshire under the new government?
Declarations of interest - knowing where you stand with people

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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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