差分

このページの2つのバージョン間の差分を表示します。

--- python:f-strings [2020/03/03 04:56] – ともやん
+++ python:f-strings [2023/05/08 09:33] (現在) – ともやん
@@ 行 1: / 行 1: @@
-====== フォーマット済み文字列リテラル(f-strings) ======
+====== フォーマット済み文字列リテラル (f-strings) ======
+<WRAP mincode>
 <code python>
-str_val = 'abc'
+>>> str_val = 'abc'
-f'{str_val:>6}'
+>>> f'{str_val:>6}'
 '   abc'
-pi = 3.14159265358979
+>>> pi = 3.14159265358979
-f'pi: {pi:.2f}'
+>>> f'pi: {pi:.2f}'
 'pi: 3.14'
-f'pi: {pi:6.3f}'
+>>> f'pi: {pi:6.3f}'
 'pi:  3.142'
-<code>
+>>> flt_val = 123456789.0123456
+>>> f'float value: {flt_val:,.4f}'
+'float value: 123,456,789.0123'
+>>> flt_val = 1234.5678
+>>> f'float value: {flt_val:>10,.2f}'
+'float value:   1,234.57'
+>>> f'float value: {flt_val:>14,.6f}'
+'float value:   1,234.567800'
+>>> 'int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}'.format(65536)
+'int: 65536; hex: 0x10000; oct: 0o200000; bin: 0b10000000000000000'
+>>> str = ' title '
+>>> f'{str:->20}'
+'------------- title '
+>>> f'{str:-^20}'
+'------ title -------'
+>>> f'{str:-<20}'
+' title -------------'
+>>>
+</code>
+</WRAP>
+===== 書式編集のパフォーマンス比較 =====
+<WRAP mincode_long>
+<code python>
+$ python
+Python 3.11.3 (main, Apr  5 2023, 00:00:00) [GCC 13.0.1 20230401 (Red Hat 13.0.1-0)] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import timeit
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... f'{name} is {age}.'""", number = 10000000)
+.247387803014135
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... '%s is %s.' % (name, age)""", number = 10000000)
+.269912829011446
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... '{} is {}.'.format(name, age)""", number = 10000000)
+.426570633018855
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... '{0} is {1}.'.format(name, age)""", number = 10000000)
+.005730772012612
+>>> ^D
+$ python
+Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:37:02) [MSC v.1924 64 bit (AMD64)] on win32
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import timeit
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... f'{name} is {age}.'""", number = 1000000)
+.2775605999999584
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... '%s is %s.' % (name, age)""", number = 1000000)
+.36503240000001824
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... '{} is {}.'.format(name, age)""", number = 1000000)
+.4583815999999956
+>>> timeit.timeit("""name = "TomoYan";age = 99;
+... '{0} is {1}.'.format(name, age)""", number = 1000000)
+>>>
+</code>
+</WRAP>
+※**f-strings** の書式編集がもっとも高速である。\\
+※次に、従来からの **%** 構文の書式編集、**{}** の置換フィールド、**{0}** の置換フィールド(インデックス番号)と続く。\\
 ===== 参考文献 =====
 [[https://docs.python.org/ja/3/reference/lexical_analysis.html#formatted-string-literals|Pythonドキュメント 字句解析 - フォーマット済み文字列リテラル]]\\
 [[https://qiita.com/QUANON/items/77ce3a9e7e33dbed489b|f-strings の使用例 - Qiita]]\\
+[[https://qiita.com/tomotaka_ito/items/594ee1396cf982ba9887|Python文字列操作マスター - Qiita]]\\
+[[https://realpython.com/python-f-strings/|Python 3's f-Strings: An Improved String Formatting Syntax (Guide) – Real Python]]\\
+[[https://pyformat.info/|PyFormat: Using % and .format() for great good!]]\\