{"id":4585,"date":"2020-03-30T16:08:51","date_gmt":"2020-03-30T16:08:51","guid":{"rendered":"https:\/\/www.askpython.com\/?p=4585"},"modified":"2023-02-16T19:57:08","modified_gmt":"2023-02-16T19:57:08","slug":"python-f-string","status":"publish","type":"post","link":"https:\/\/www.askpython.com\/python\/string\/python-f-string","title":{"rendered":"Understanding Python f-string"},"content":{"rendered":"\n

String formatting in Python can be achieved using f-string. Thus, in this article, we will be focusing on the implementation of Python f-string.<\/p>\n\n\n\n

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Necessity of f-string in Python<\/h2>\n\n\n\n

Python f-string basically serves the purpose of string formatting. Before the emergence of “f-strings”, we had the following ways to format strings in Python:<\/p>\n\n\n\n

1.<\/strong> Python ‘%’ operator<\/strong> — <\/p>\n\n\n\n

Disadvantage<\/strong>: Python % operator<\/code> cannot be used with Objects and attributes.<\/p>\n\n\n\n

2. <\/strong>Python format() function —<\/p>\n\n\n\n

Disadvantage<\/strong>: The string.format() function<\/code> could overcome the drawback of ‘%’ operator, but it proved out to be a verbose <\/strong>way of formatting.<\/p>\n\n\n\n

Thus, Python f-string <\/strong>came into existence wherein the strings can be interpolated and formatted with much simpler and minimal syntax<\/strong>. The strings are formatted at runtime<\/strong> by the Python interpreter.<\/p>\n\n\n\n

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Working of Python f-string with examples<\/h2>\n\n\n\n

The f-string also known as formatted strings serves the purpose of Literal String Interpolation <\/strong>i.e. injection of strings and formatting of the particular string.<\/p>\n\n\n\n

Syntax:<\/strong><\/p>\n\n\n

\nf'{string}'\n<\/pre><\/div>\n\n\n
Example:<\/strong> f-string with string as an iterable<\/strong><\/p>\n\n\n
\nstr1 = 'Python'\n\nstr4 = 'JournalDev'\n\nres = f'{str4} provides tutorials on {str1}'\n\nprint(res)\n<\/pre><\/div>\n\n\n
As clearly seen above, f-string is used to inject <\/strong>or interpolate <\/strong>the input string str1 <\/strong>and str4 <\/strong>between the string statement.<\/p>\n\n\n\n
Output:<\/strong><\/p>\n\n\n
\nJournalDev provides tutorials on Python\n<\/pre><\/div>\n\n\n
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Python f-string with raw strings<\/h3>\n\n\n\n
Python raw strings basically treat the special characters considered as ‘escape sequences’ as literal characters<\/strong>. It is used when we want the escape sequences i.e. ‘\\n’<\/strong> or backslash(\\)<\/strong> as literal sequences of characters.<\/p>\n\n\n\n
Syntax: Python raw strings<\/strong><\/p>\n\n\n
\nr'string'\n<\/pre><\/div>\n\n\n
Python f-strings can work well simultaneously with the raw strings.<\/p>\n\n\n\n
Syntax: f-string along with raw strings<\/strong><\/p>\n\n\n
\nfr'string or {string}'\n<\/pre><\/div>\n\n\n
Example:<\/strong><\/p>\n\n\n
\nstr1 = 'Python'\n\nstr4 = 'JournalDev'\n\nres = fr'{str4} \\n and AskPython provides tutorials on {str1}'\n\nprint(res)      \n\n<\/pre><\/div>\n\n\n
In the above example, ‘\\n’ is treated as a literal character.<\/p>\n\n\n\n
Output:<\/strong><\/p>\n\n\n
\nJournalDev \\n and AskPython provides tutorials on Python\n<\/pre><\/div>\n\n\n
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Calling functions with f-string <\/h3>\n\n\n\n
Python f-strings enables us to call functions<\/a> within it. Thus, optimizing the code to an extent. The same way can be used for creating lambda functions within f-string bracets.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n
\nf'{func()}'\n<\/pre><\/div>\n\n\n
Example:<\/strong><\/p>\n\n\n
\ndef mult(a,b):\n    res = a*b\n    return res\n\nmult_res = f'{mult(10,20)}'\nprint(mult_res)\n<\/pre><\/div>\n\n\n
Output:<\/strong><\/p>\n\n\n
\n200\n<\/pre><\/div>\n\n\n
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Python f-string with blank\/white-spaces<\/h3>\n\n\n\n
Python f-strings can also work with blank or white-spaces<\/strong>. It ignores the trailing and the leading white-spaces <\/strong>and the spaces between the literal string are unaltered<\/strong> and preserved<\/strong>.<\/p>\n\n\n\n
Example:<\/strong><\/p>\n\n\n
\nmult_res = f'  Multiplication: { 10 * 10 }  '\nprint(mult_res)\n<\/pre><\/div>\n\n\n
Output:<\/strong><\/p>\n\n\n
\n  Multiplication: 100  \n<\/pre><\/div>\n\n\n
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Python f-string with expressions<\/h3>\n\n\n\n
Python f-string can work with expressions<\/strong>. Thus, basic manipulations can be performed directly within f-string.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n
\nf'{expression'}\n<\/pre><\/div>\n\n\n
Example:<\/strong><\/p>\n\n\n
\nx = 10\ny = 5\nprint(f'Result: {x\/y} ')\n\n<\/pre><\/div>\n\n\n
Output:<\/strong><\/p>\n\n\n
\nResult: 2.0 \n<\/pre><\/div>\n\n\n
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f-string with a Python dictionary<\/h3>\n\n\n\n
As we all know, Python dictionary<\/a> data structure works with key-value pairs. Python f-string can also be framed along with the dictionaries.<\/p>\n\n\n\n
Syntax:<\/strong><\/p>\n\n\n
\nf"{dict['key']}"\n<\/pre><\/div>\n\n\n
Example:<\/strong><\/p>\n\n\n
\ninfo = {'age':'21', 'city':'Pune'}\n\nprint(f"{info['city']}")\n<\/pre><\/div>\n\n\n
Output:<\/strong><\/p>\n\n\n
\nPune\n<\/pre><\/div>\n\n\n
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Conclusion<\/h2>\n\n\n\n
Thus, in this article, we have understood the necessity and working of f-string with various iterables and expressions.<\/p>\n\n\n\n
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References<\/h2>\n\n\n\n