التعابير المنتظمة في بايثون بيثون Python Regular Expressions
التعابير المنتظمة في بايثون بيثون
Python Regular Expressions
التعابير المنتظمة في بايثون بيثون Python Regular Expressions
التعبير العادي عبارة عن تسلسل خاص من الأحرف يساعدك على مطابقة أو إيجاد سلاسل أو مجموعات أخرى من السلاسل ، باستخدام بناء جملة متخصص محتفظ به في نمط. التعبيرات العادية تستخدم على نطاق واسع في عالم UNIX.
توفر الوحدة النمطية Python دعما كاملا للتعبيرات العادية التي تشبه Perl في Python. الوحدة النمطية re تثير re.error الاستثناء إذا حدث خطأ أثناء ترجمة أو استخدام تعبير عادي.
سوف نغطي وظيفتين مهمتين ، والتي سيتم استخدامها للتعامل مع التعبيرات العادية. لكن الشيء الصغير أولاً: هناك العديد من الشخصيات ، والتي سيكون لها معنى خاص عند استخدامها في التعبير العادي. لتجنب أي تشويش أثناء التعامل مع التعبيرات المعتادة ، نستخدم Raw Strings كـ r'expression.
The match Function دالة التطابق
تحاول هذه الوظيفة او الدالة التطابق
RE نمط إلى سلسلة مع أعلام اختياري.
فيما يلي بناء الجملة لهذه الوظيفة -
re.match(pattern, string, flags=0)
الرقم | الوسيط والوصف |
---|---|
1 |
pattern
هذا هو التعبير المنتظم المراد مطابقته.
|
2 |
string
هذه هي السلسلة التي سيتم البحث فيها لمطابقة النمط في بداية السلسلة.
|
3 |
flags
يمكنك تحديد إشارات مختلفة باستخدام bitwise OR (|). هذه هي المعدلات ، والتي يتم سردها في الجدول أدناه.
|
ترجع الدالة re.match كائن تطابق عند النجاح ، بلا بلا فشل. نحن نستخدم وظيفة group (num) أو groups () لكائن المطابقة للحصول على تعبير مطابق.
الرقم. | تطابق طريقة الكائن والوصف |
---|---|
1 |
group(num=0)
تُرجع هذه الطريقة المطابقة بأكملها (أو مجموعة فرعية محددة)
|
2 |
groups()
تُرجع هذه الطريقة جميع المجموعات الفرعية المتطابقة في فئة (فارغة إن لم تكن موجودة)
|
مثال Example
#!/usr/bin/python import re line = "Cats are smarter than dogs" matchObj = re.match( r'(.*) are (.*?) .*', line, re.M|re.I) if matchObj: print "matchObj.group() : ", matchObj.group() print "matchObj.group(1) : ", matchObj.group(1) print "matchObj.group(2) : ", matchObj.group(2) else: print "No match!!"
المخرجات
matchObj.group() : Cats are smarter than dogs matchObj.group(1) : Cats matchObj.group(2) : smarter
The search Function دالة البحث
تبحث هذه الوظيفة عن التواجد الأول لنموذج RE داخل السلسلة مع الأعلام الاختيارية.
فيما يلي بناء الجملة لهذه الوظيفة -
re.search(pattern, string, flags=0)
هنا هو وصف المعلمات -
الرقم | المعلمات او الوسيطات والوصف |
---|---|
1 |
pattern
هذا هو التعبير المنتظم المراد مطابقته.
|
2 |
string
هذه هي السلسلة التي سيتم البحث فيها لمطابقة النموذج في أي مكان في السلسلة.
|
3 |
flags
يمكنك تحديد إشارات مختلفة باستخدام bitwise OR (|). هذه هي المعدلات ، والتي يتم سردها في الجدول أدناه.
|
ترجع الدالة re.search كائن تطابق عند النجاح ، ولا شيء عند الفشل. نحن نستخدم وظيفة group (num) أو groups () لكائن المطابقة للحصول على تعبير مطابق.
الرقم. | تطابق أساليب الكائن والوصف |
---|---|
1 |
group(num=0)
This method returns entire match (or specific subgroup num)
|
2 |
groups()
This method returns all matching subgroups in a tuple (empty if there weren't any)
|
Example
#!/usr/bin/python import re line = "Cats are smarter than dogs"; searchObj = re.search( r'(.*) are (.*?) .*', line, re.M|re.I) if searchObj: print "searchObj.group() : ", searchObj.group() print "searchObj.group(1) : ", searchObj.group(1) print "searchObj.group(2) : ", searchObj.group(2) else: print "Nothing found!!"
When the above code is executed, it produces following result −
searchObj.group() : Cats are smarter than dogs searchObj.group(1) : Cats searchObj.group(2) : smarter
Matching Versus Searching
Python offers two different primitive operations based on regular expressions: matchchecks for a match only at the beginning of the string, while search checks for a match anywhere in the string (this is what Perl does by default).
Example
#!/usr/bin/python import re line = "Cats are smarter than dogs"; matchObj = re.match( r'dogs', line, re.M|re.I) if matchObj: print "match --> matchObj.group() : ", matchObj.group() else: print "No match!!" searchObj = re.search( r'dogs', line, re.M|re.I) if searchObj: print "search --> searchObj.group() : ", searchObj.group() else: print "Nothing found!!"
When the above code is executed, it produces the following result −
No match!! search --> searchObj.group() : dogs
Search and Replace
One of the most important re methods that use regular expressions is sub.
Syntax
re.sub(pattern, repl, string, max=0)
This method replaces all occurrences of the RE pattern in string with repl, substituting all occurrences unless max provided. This method returns modified string.
Example
#!/usr/bin/python import re phone = "2004-959-559 # This is Phone Number" # Delete Python-style comments num = re.sub(r'#.*$', "", phone) print "Phone Num : ", num # Remove anything other than digits num = re.sub(r'\D', "", phone) print "Phone Num : ", num
When the above code is executed, it produces the following result −
Phone Num : 2004-959-559 Phone Num : 2004959559
Regular Expression Modifiers: Option Flags
Regular expression literals may include an optional modifier to control various aspects of matching. The modifiers are specified as an optional flag. You can provide multiple modifiers using exclusive OR (|), as shown previously and may be represented by one of these −
Sr.No. | Modifier & Description |
---|---|
1 |
re.I
Performs case-insensitive matching.
|
2 |
re.L
Interprets words according to the current locale. This interpretation affects the alphabetic group (\w and \W), as well as word boundary behavior(\b and \B).
|
3 |
re.M
Makes $ match the end of a line (not just the end of the string) and makes ^ match the start of any line (not just the start of the string).
|
4 |
re.S
Makes a period (dot) match any character, including a newline.
|
5 |
re.U
Interprets letters according to the Unicode character set. This flag affects the behavior of \w, \W, \b, \B.
|
6 |
re.X
Permits "cuter" regular expression syntax. It ignores whitespace (except inside a set [] or when escaped by a backslash) and treats unescaped # as a comment marker.
|
Regular Expression Patterns
Except for control characters, (+ ? . * ^ $ ( ) [ ] { } | \), all characters match themselves. You can escape a control character by preceding it with a backslash.
Following table lists the regular expression syntax that is available in Python −
Sr.No. | Pattern & Description |
---|---|
1 |
^
Matches beginning of line.
|
2 |
$
Matches end of line.
|
3 |
.
Matches any single character except newline. Using m option allows it to match newline as well.
|
4 |
[...]
Matches any single character in brackets.
|
5 |
[^...]
Matches any single character not in brackets
|
6 |
re*
Matches 0 or more occurrences of preceding expression.
|
7 |
re+
Matches 1 or more occurrence of preceding expression.
|
8 |
re?
Matches 0 or 1 occurrence of preceding expression.
|
9 |
re{ n}
Matches exactly n number of occurrences of preceding expression.
|
10 |
re{ n,}
Matches n or more occurrences of preceding expression.
|
11 |
re{ n, m}
Matches at least n and at most m occurrences of preceding expression.
|
12 |
a| b
Matches either a or b.
|
13 |
(re)
Groups regular expressions and remembers matched text.
|
14 |
(?imx)
Temporarily toggles on i, m, or x options within a regular expression. If in parentheses, only that area is affected.
|
15 |
(?-imx)
Temporarily toggles off i, m, or x options within a regular expression. If in parentheses, only that area is affected.
|
16 |
(?: re)
Groups regular expressions without remembering matched text.
|
17 |
(?imx: re)
Temporarily toggles on i, m, or x options within parentheses.
|
18 |
(?-imx: re)
Temporarily toggles off i, m, or x options within parentheses.
|
19 |
(?#...)
Comment.
|
20 |
(?= re)
Specifies position using a pattern. Doesn't have a range.
|
21 |
(?! re)
Specifies position using pattern negation. Doesn't have a range.
|
22 |
(?> re)
Matches independent pattern without backtracking.
|
23 |
\w
Matches word characters.
|
24 |
\W
Matches nonword characters.
|
25 |
\s
Matches whitespace. Equivalent to [\t\n\r\f].
|
26 |
\S
Matches nonwhitespace.
|
27 |
\d
Matches digits. Equivalent to [0-9].
|
28 |
\D
Matches nondigits.
|
29 |
\A
Matches beginning of string.
|
30 |
\Z
Matches end of string. If a newline exists, it matches just before newline.
|
31 |
\z
Matches end of string.
|
32 |
\G
Matches point where last match finished.
|
33 |
\b
Matches word boundaries when outside brackets. Matches backspace (0x08) when inside brackets.
|
34 |
\B
Matches nonword boundaries.
|
35 |
\n, \t, etc.
Matches newlines, carriage returns, tabs, etc.
|
36 |
\1...\9
Matches nth grouped subexpression.
|
37 |
\10
Matches nth grouped subexpression if it matched already. Otherwise refers to the octal representation of a character code.
|
Regular Expression Examples
Literal characters
Sr.No. | Example & Description |
---|---|
1 |
python
Match "python".
|
Character classes
Sr.No. | Example & Description |
---|---|
1 |
[Pp]ython
Match "Python" or "python"
|
2 |
rub[ye]
Match "ruby" or "rube"
|
3 |
[aeiou]
Match any one lowercase vowel
|
4 |
[0-9]
Match any digit; same as [0123456789]
|
5 |
[a-z]
Match any lowercase ASCII letter
|
6 |
[A-Z]
Match any uppercase ASCII letter
|
7 |
[a-zA-Z0-9]
Match any of the above
|
8 |
[^aeiou]
Match anything other than a lowercase vowel
|
9 |
[^0-9]
Match anything other than a digit
|
Special Character Classes
Sr.No. | Example & Description |
---|---|
1 |
.
Match any character except newline
|
2 |
\d
Match a digit: [0-9]
|
3 |
\D
Match a nondigit: [^0-9]
|
4 |
\s
Match a whitespace character: [ \t\r\n\f]
|
5 |
\S
Match nonwhitespace: [^ \t\r\n\f]
|
6 |
\w
Match a single word character: [A-Za-z0-9_]
|
7 |
\W
Match a nonword character: [^A-Za-z0-9_]
|
Repetition Cases
Sr.No. | Example & Description |
---|---|
1 |
ruby?
Match "rub" or "ruby": the y is optional
|
2 |
ruby*
Match "rub" plus 0 or more ys
|
3 |
ruby+
Match "rub" plus 1 or more ys
|
4 |
\d{3}
Match exactly 3 digits
|
5 |
\d{3,}
Match 3 or more digits
|
6 |
\d{3,5}
Match 3, 4, or 5 digits
|
Nongreedy repetition
This matches the smallest number of repetitions −
Sr.No. | Example & Description |
---|---|
1 |
<.*>
Greedy repetition: matches "
|
2 |
<.*?>
Nongreedy: matches "
|
Grouping with Parentheses
Sr.No. | Example & Description |
---|---|
1 |
\D\d+
No group: + repeats \d
|
2 |
(\D\d)+
Grouped: + repeats \D\d pair
|
3 |
([Pp]ython(, )?)+
Match "Python", "Python, python, python", etc.
|
Backreferences
This matches a previously matched group again −
Sr.No. | Example & Description |
---|---|
1 |
([Pp])ython&\1ails
Match python&pails or Python&Pails
|
2 |
(['"])[^\1]*\1
Single or double-quoted string. \1 matches whatever the 1st group matched. \2 matches whatever the 2nd group matched, etc.
|
Alternatives
Sr.No. | Example & Description |
---|---|
1 |
python|perl
Match "python" or "perl"
|
2 |
rub(y|le))
Match "ruby" or "ruble"
|
3 |
Python(!+|\?)
"Python" followed by one or more ! or one ?
|
Anchors
This needs to specify match position.
Sr.No. | Example & Description |
---|---|
1 |
^Python
Match "Python" at the start of a string or internal line
|
2 |
Python$
Match "Python" at the end of a string or line
|
3 |
\APython
Match "Python" at the start of a string
|
4 |
Python\Z
Match "Python" at the end of a string
|
5 |
\bPython\b
Match "Python" at a word boundary
|
6 |
\brub\B
\B is nonword boundary: match "rub" in "rube" and "ruby" but not alone
|
7 |
Python(?=!)
Match "Python", if followed by an exclamation point.
|
8 |
Python(?!!)
Match "Python", if not followed by an exclamation point.
|
Special Syntax with Parentheses
Sr.No. | Example & Description |
---|---|
1 |
R(?#comment)
Matches "R". All the rest is a comment
|
2 |
R(?i)uby
Case-insensitive while matching "uby"
|
3 |
R(?i:uby)
Same as above
|
4 |
rub(?:y|le))
Group only without creating \1 backreference
|
التسميات: Python بايثون
<< الصفحة الرئيسية