{"id":3810,"date":"2018-07-22T23:12:00","date_gmt":"2018-07-22T17:42:00","guid":{"rendered":"https:\/\/www.csestack.org\/?p=3810"},"modified":"2019-03-16T17:36:41","modified_gmt":"2019-03-16T12:06:41","slug":"python-string-formatting","status":"publish","type":"post","link":"https:\/\/www.csestack.org\/python-string-formatting\/","title":{"rendered":"4 Python String Formatting Every Python Developer should Master"},"content":{"rendered":"

Coming so far with programming, we know, the string is a set of characters. And no doubt, it is one of the most useful data types in any programming language.<\/p>\n

What is Python String Formatting?<\/strong><\/p>\n

Instead of using a string as it is, many times we need to stuff the string with other data value. And it is called as string formatting.<\/p>\n

You will learn more about it as I explain string formatting with an example below.<\/p>\n

In this tutorial, you will also learn to use different approaches for string formatting in Python.<\/p>\n

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Table of contents<\/strong><\/p>\n

    \n
  1. String Formatting using %\u00a0Operator<\/a><\/li>\n
  2. String Formatting using str.format()<\/a><\/li>\n
  3. (Python 3.6+) String Formatting using f-Strings<\/a><\/li>\n
  4. Template Strings (Standard Library)<\/a><\/li>\n<\/ol>\n<\/div>\n

    To make the best use of this tutorial and mastering string formatting, open your Python interpreter and try running commands as we go with this tutorial.<\/p>\n

    So, without squandering any further time, let’s discuss now.<\/p>\n

    1) String Formatting using %\u00a0Operator<\/h4>\n

    This is the oldest string formatting method.<\/p>\n

    >>> lang = 'Python'\r\n>>>'You are working with %s' % lang\r\n\"You are working with Python\"<\/pre>\n
    Here, we are substituting string value. %s is a format specifier for\u00a0string\u00a0data. Other than string, you can substitute any other data types as well.<\/p>\n
    Below is an example where the hexadecimal value is substituted.<\/p>\n
    >>> noErr = 45565\r\n>>> '%x' % errno\r\n'b1fd'<\/pre>\n
    %x is a format specifier for hexadecimal data. With this format specifier, you can convert an integer value into the hex decimal value and then formate it into the string.<\/p>\n
    Always print hexadecimal values in the\u00a0standard format by appending “0x” before the hexadecimal string. It makes easy for the end user to identify the formatting of data value.<\/p>\n
    If there are multiple substitutions or if you want to stuff multiple values into the single string, you need to pass those values as tuple elements.<\/p>\n
    >>> lang = 'Python'\r\n>>> noErr = 45565\r\n>>> 'You are working with %s. Please refer 0x%x error.' % (lang, noErr)\r\n'You are working with Python. Please refer 0xb1fd error.'<\/pre>\n
    You can also pass multiple substitute variables using dictionary name-value pair.<\/p>\n
    >>> lang = 'Python'\r\n>>> noErr = 45565\r\n>>> 'You are working with %(lang)s. Please refer 0x%(noErr)x error.' % {\r\n... \"lang\": lang, \"noErr\": noErr}\r\n'You are working with Python. Please refer 0xb1fd error.'<\/pre>\n
    Here you don’t need to worry about the sequence of substitute variables.<\/p>\n
    2) String Formatting using str.format()<\/h4>\n
    You can call the format method using the str string object.<\/p>\n
    >>> lang = 'Python'\r\n>>> ''You are working with\u00a0 {}'.format(lang)\r\n'You are working with Python'<\/pre>\n
    With this approach, passing the name-value pairs as an argument to the format method is easy.<\/p>\n
    >>> lang = 'Python'\r\n>>> noErr = 45565\r\n>>> 'You are working with {lang}. Please refer {noErr:x} error.'.format(\u00a0\r\n... lang=lang, noErr=noErr)\r\n'You are working with Python. Please refer 0xb1fd error.'<\/pre>\n
    3) String Formatting using f-Strings (Python 3.6+)<\/h4>\n
    It is also called as String Interpolation.<\/p>\n
    Note:<\/strong> f-string formatting<\/a> approach is new. And it only works with the Python 3 having version 3.6 or higher.<\/p>\n
    >>> lang = 'Python'\r\n>>> f'You are working with {lang}.'\r\nYou are working with Python.<\/pre>\n
    How to Evaluate\u00a0Expression in Python String Formatting?<\/strong><\/p>\n
    You can also evaluate mathematical operations inside the f-string. It is more like embedding Python expressions inside the string to evaluate and print the result.<\/p>\n
    >>> p = 11\r\n>>> q = 9\r\n>>> f'Addition of two number is {p + q} and multiplication is {p * q}.'\r\nAddition of two number is 20 and multiplication is 99.'<\/pre>\n
    If you need to evaluate numerical\u00a0data types<\/a>\u00a0expression and substitute result\u00a0into the string, use this method.<\/p>\n
    4) Template Strings (Standard Library)<\/h4>\n
    So another approach you can use and it is\u00a0called as\u00a0a template string. You need to import the Template module from a string.<\/p>\n
    First, make the template object using Template(). You can format the substitution variable names by prefixing $ sign. And then substitute the value for the variable.<\/p>\n
    >>> name = Alice\r\n>>> from string import Template\r\n>>> t = Template('My name is $name.')\r\n>>> t.substitute(name=name)\r\n'My name is Alice.'<\/pre>\n
    That’s it all from\u00a0Python string formatting tutorial. If you give an attention and try to run commands for each formatting approach, this topic is not much difficult.<\/p>\n
    Other Python String Tutorials:<\/strong><\/p>\n