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Q&A Why does my regex "match" at the beginning of the string, but not at the end?

My impression is that the regexps behave a little bit odd: >>> import re >>> r=re.compile("test") >>> r.match("test") <re.Match object; span=(0, 4), match='test'&g...

2 answers · posted 1y ago by peterh‭ · last activity 5mo ago by Karl Knechtel‭

Question regex python-3

#2: Post edited by

Karl Knechtel‭ · 2026-04-15T19:46:26Z (5 months ago)
Copyedit for clarity; add link for the third-party package tested; give a sensible title

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~~Why python regexps look expecting a begin match, but not an ending one?~~

Why does my regex "match" at the beginning of the string, but not at the end?

My impression is that the regexps behave a little bit odd:
```
>>> import re
>>> r=re.compile("test")
>>> r.match("test")
<re.Match object; span=(0, 4), match='test'>
>>> r.match("1test")
>>> r.match("test2")
<re.Match object; span=(0, 4), match='test'>
>>> r.match("1test2")
>>>
```
I have also tried python-pcre, it behaves on the same way. If the "regexp" is only a single word, it should behave as a substring match (or a full-line match). It seems matching lines starting with "test", but not the ones ending with it (or containining it somewhere).
Why?

My impression is that the regexps behave a little bit odd:
```
>>> import re
>>> r=re.compile("test")
>>> r.match("test")
<re.Match object; span=(0, 4), match='test'>
>>> r.match("1test")
>>> r.match("test2")
<re.Match object; span=(0, 4), match='test'>
>>> r.match("1test2")
>>>
```
I also tried using [python-pcre](https://pypi.org/project/python-pcre/) and got the same results.
The regex is just an ordinary word, so I think this should behave like a substring match, or perhaps a full-line match. But it seems to match lines starting with "test", but not lines that have "test" somewhere else.
Why?

#1: Initial revision by

peterh‭ · 2025-06-04T11:41:34Z (over 1 year ago)

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Why python regexps look expecting a begin match, but not an ending one?

My impression is that the regexps behave a little bit odd:

```
>>> import re
>>> r=re.compile("test")
>>> r.match("test")
<re.Match object; span=(0, 4), match='test'>
>>> r.match("1test")
>>> r.match("test2")
<re.Match object; span=(0, 4), match='test'>
>>> r.match("1test2")
>>> 
```

I have also tried python-pcre, it behaves on the same way. If the "regexp" is only a single word, it should behave as a substring match (or a full-line match). It seems matching lines starting with "test", but not the ones ending with it (or containining it somewhere).

Why?

regex python-3

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