A summary of formatted output usage in Python

This example summarizes the formatted output usage in Python. Share to everyone for your reference, as follows:

Python has a total of two formatting output syntaxes.

One is similar to the C-language printf approach, called formatting Expression

>>> '%s%d-%d '% (' hello ', 7, 1)  ' Hello 7-1 '

The other is a C #-like way, called string formatting method Calls

>>> ' {0} {1}:{2} '. Format (' Hello ', ' 1 ', ' 7 ')  ' Hello 1:7 '

The first way to specify the precision of a floating-point number, such as

>>> '%.3f '% 1.234567869  ' 1.235 '

Specify the precision of floating-point numbers dynamically at run time

But how can the code specify the precision of a floating-point number dynamically through parameters when it is running?

The magic of Python is that it provides a very handy syntax. Just add a * before TypeCode (here is f), and the precision of the floating-point number is specified using the numbers in front of it.

>>> for I in range (5):  ... '%.*f '% (i, 1.234234234234234) ...  ' 1 '  1.2 '  1.23 ' 1.234 '  1.2342 '

It can be seen from the output that the precision is specified dynamically at run time, thus eliminating the patchwork of formatted strings.

Using the String formatting Method Calls can be done more cleanly.

>>> for I in range (5):  ...  ' {0:. {1}f} '. Format (1/3.0, i) ...  ' 0 '  0.3 '  0.33 ' 0.333 '  0.3333 '

Implement a simple Template tool

The template language provided by Django allows us to bind the Python variable through a dict (dictionary) HTML file, in fact, using the format output of Python we can just do a text substitution function.

>>> replay = "" "... Hello World Cup ... Germany vs Brazil ...% (Germany) d:% (Brazil) d "" "  >>> print (replay% {' Germany ': 7, ' Brazil ': 1})  Hello W Orld Cup ...  Germany vs Brazil  7:1

And you can play like this.

>>> Germany = 7  >>> Brazil = 1  >>> '% (Germany) d:% (Brazil) d '% VARs ()  ' 7:1 '

Accessing object properties and dictionary key values in a formatted string

>>> ' My {1[kind]} runs {0.platform} '. Format (sys, {' kind ': ' pc '})  ' My PC runs Linux '  >>> ' my {ma P[kind]} runs {sys.platform} '. Format (Sys=sys, map={' kind ': ' pc '})  ' My pc runs Linux '

Accessing the list element in a formatted string by subscript (positive integer)

>>> somelist = list (' SPAM ')  >>> ' first={0[0]}, third={0[2]} '. Format (somelist)  ' First=s, Third=a '  >>> ' first={0}, Last={1} '. Format (somelist[1], somelist[-1])  ' first=p, last=m '  > >> parts = somelist[0], somelist[-1], somelist[1:-1]  >>> ' first={0}, Last={1}, middle={2} '. Format (* Parts)  "First=s, Last=m, middle=[' P ', ' A ']"  >>>

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