Created
February 25, 2020 16:59
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bulk replace
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| task description: | |
| please, write a function that receives | |
| 1)path to file | |
| 2) string to replace | |
| 3) the new string to replace with | |
| 4) in which line in the file to replace (if empty, then replace all) | |
| I assume new string should not be same with pattern | |
| Line number it's a real number (starts from 1). For example client see in text editor this number and pass it to func. I | |
| will switch it to index (as it's starts from 0) | |
| I wrapped it's to try/except with custom exception because in this way exceptions more clear and I can manage it. | |
| I added helper function for write lines because do not necessary write same code twice. | |
| There also possible to use fileinput standard library (https://docs.python.org/3/library/fileinput.html). | |
| But as multiple files wasn't in requirements I used open() as docs said "If you just want to read or write one file | |
| see open()." |
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| import unittest | |
| from util import bulk_replace, UtilException | |
| class UtilTestCases(unittest.TestCase): | |
| def setUp(self): | |
| self.filepath = 'test_text' | |
| self.pattern = 'foo' | |
| self.replace_with = 'bar' | |
| def test_same_patterns(self): | |
| try: | |
| bulk_replace(filepath=self.filepath, pattern=self.pattern, replace_with='foo') | |
| except UtilException as e: | |
| self.assertEqual(e.__str__(), 'pattern and replace_with can not be same') | |
| def test_line(self): | |
| try: | |
| bulk_replace(filepath=self.filepath, pattern=self.pattern, replace_with=self.replace_with, line=999) | |
| except UtilException as e: | |
| self.assertEqual(e.__str__(), 'line not found') | |
| try: | |
| bulk_replace(filepath=self.filepath, pattern=self.pattern, replace_with=self.replace_with, line=-1) | |
| except UtilException as e: | |
| self.assertEqual(e.__str__(), 'line index should be gte 1') | |
| def test_replace_one_line(self): | |
| bulk_replace(filepath=self.filepath, pattern=self.pattern, replace_with=self.replace_with, line=1) | |
| file = open(self.filepath, 'r') | |
| line = file.readlines() | |
| file.close() | |
| self.assertEqual(line[0].strip('\n'), self.replace_with) | |
| # switch it back | |
| bulk_replace(filepath=self.filepath, pattern=self.replace_with, replace_with=self.pattern, line=1) | |
| def test_replace_all(self): | |
| file = open(self.filepath, 'r') | |
| old = file.readlines() | |
| file.close() | |
| bulk_replace(filepath=self.filepath, pattern=self.pattern, replace_with=self.replace_with) | |
| file = open(self.filepath, 'r') | |
| lines = file.readlines() | |
| self.assertTrue(self.pattern not in lines) | |
| # switch it back | |
| file = open(self.filepath, 'w') | |
| file.writelines(old) | |
| file.close() | |
| if __name__ == '__main__': | |
| unittest.main() |
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| foo | |
| bar | |
| foo-bar | |
| bar-foo-bar | |
| foo-bar-bar |
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| class UtilException(Exception): | |
| pass | |
| def bulk_replace(filepath, pattern, replace_with, line=None): | |
| """ | |
| Function which open file, find necessary pattern and replace it with new fragment. | |
| :param filepath: Path to file | |
| :param pattern: String to replace | |
| :param replace_with: The new string to replace with | |
| :param line: In which line in the file to replace (if empty, then replace all) | |
| :return: | |
| """ | |
| try: | |
| assert pattern != replace_with | |
| except AssertionError: | |
| raise UtilException('pattern and replace_with can not be same') | |
| with open(filepath, 'r') as f: | |
| text = f.readlines() | |
| f.close() | |
| if line: # assume we get line number, not index | |
| try: | |
| assert line >= 1 | |
| try: | |
| # replace necessary text | |
| text[line-1] = text[line-1].replace(pattern, replace_with) | |
| _write_lines(filepath, text) | |
| except IndexError: | |
| raise UtilException('line not found') | |
| except AssertionError: | |
| raise UtilException('line index should be gte 1') | |
| else: | |
| # walk through all lines and replace necessary text | |
| lines = [line.replace(pattern, replace_with) for line in text] | |
| _write_lines(filepath, lines) | |
| def _write_lines(filepath, lines): | |
| """ | |
| Helper function | |
| :param filepath: File path to open | |
| :param lines: list of lines | |
| :return: | |
| """ | |
| with open(filepath, 'w') as f: | |
| f.writelines(lines) | |
| f.close() |
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