Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit d1000be

Browse files
Regular expression Tutorial - begineer level with more infomation
1 parent f9ddff6 commit d1000be

File tree

1 file changed

+320
-0
lines changed

1 file changed

+320
-0
lines changed

‎RE/BeginerLevel.py

Lines changed: 320 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,320 @@
1+
'''
2+
Ram, consider this file as beginer level tutorial kinda things.
3+
you will learn about regular expressions (RegEx), and use Python's re module to work with RegEx (with the help of examples).
4+
5+
A Regular Expression (RegEx) is a sequence of characters that defines a search pattern.
6+
7+
'''
8+
# below line a regex pattern
9+
example_pattern = '^a...s$'
10+
11+
# What can we do with this above pattern?
12+
# What did you understand when you read this pattern?
13+
14+
# Matching Patterns with example..
15+
16+
# Expression String Matched
17+
# ^a...s$ abs No match
18+
# alias Match
19+
# abyss Match
20+
# Alias No match
21+
# An abacus No match
22+
23+
24+
# Code Implementation example,
25+
26+
import re # re is the pre-defined module that exist inside Python
27+
28+
sample_test_string = 'Sanjay is conducting a session to Ram alias prrampalli who is residing in London'
29+
sample_focused_string = "abyss"
30+
31+
result = re.match(example_pattern, sample_focused_string)
32+
print(result)
33+
34+
if result:
35+
print("Search successful.")
36+
else:
37+
print("Search unsuccessful.")
38+
39+
40+
# from the above example, we used re.match() to check string match, there're other method under re, those are,
41+
# re.compile
42+
# re.sub
43+
# re.search
44+
# re.findall
45+
# re.split
46+
47+
# To specify regular expressions, metacharacters are used. In the above example, ^ and $ are metacharacters
48+
49+
'''
50+
What is meta characters?
51+
52+
Metacharacters are characters that are interpreted in a special way by a RegEx engine. Here's a list of metacharacters:
53+
54+
[] . ^ $ * + ? {} () \ |
55+
56+
'''
57+
58+
# 1 - We can discuss about []
59+
60+
# Expression String Matched?
61+
# [abc] a 1 match
62+
# ac 2 matches
63+
# Hey Jude No match
64+
# abc de ca 5 matches
65+
66+
# [abc] will match if the string you are trying to match contains any of the a, b or c.
67+
68+
# You can also specify a range of characters using - inside square brackets.
69+
70+
# [a-e] is the same as [abcde].
71+
# [1-4] is the same as [1234].
72+
# [0-39] is the same as [01239]. **
73+
74+
# You can complement (invert) the character set by using caret ^ symbol at the start of a square-bracket.
75+
76+
# [^abc] means any character except a or b or c.
77+
# [^0-9] means any non-digit character.
78+
79+
80+
81+
# 2 - We can now discuss about .
82+
83+
'''
84+
. -> called as period
85+
86+
A period matches any single character (except newline '\n').
87+
88+
Expression String Matched?
89+
.. a No match
90+
ac 1 match
91+
acd 1 match
92+
acde 2 matches (contains 4 characters)
93+
94+
'''
95+
96+
# 3 - We can discuss about Carret.
97+
98+
'''
99+
^ - Caret
100+
101+
The caret symbol ^ is used to check if a string starts with a certain character.
102+
103+
Expression String Matched?
104+
^a a 1 match
105+
abc 1 match
106+
bac No match
107+
^ab abc 1 match
108+
acb No match (starts with a but not followed by b)
109+
110+
'''
111+
112+
# 4 - We can look into $
113+
114+
'''
115+
$ - Dollar
116+
117+
The dollar symbol $ is used to check if a string ends with a certain character.
118+
119+
Expression String Matched?
120+
a$ a 1 match
121+
formula 1 match
122+
cab No match
123+
ram No Match
124+
ra 1 Match
125+
'''
126+
127+
128+
# 5 - Astriek or star
129+
130+
'''
131+
* - Star
132+
133+
The star symbol * matches zero or more occurrences of the pattern left to it.
134+
135+
Expression String Matched?
136+
ma*n mn 1 match
137+
man 1 match
138+
maaan 1 match
139+
main No match (a is not followed by n)
140+
woman 1 match
141+
ran No match
142+
ram No Match
143+
maen No Match
144+
maaaaaaan 1 Match
145+
'''
146+
147+
# 6 - Plus
148+
'''
149+
+ - Plus
150+
151+
The plus symbol + matches one or more occurrences of the pattern left to it.
152+
153+
Expression String Matched?
154+
ma+n mn No match (no a character)
155+
man 1 match
156+
maaan 1 match
157+
main No match (a is not followed by n)
158+
woman 1 match
159+
'''
160+
161+
# 7 - ? - Question Mark
162+
'''
163+
The question mark symbol ? matches zero or one occurrence of the pattern left to it.
164+
165+
Expression String Matched?
166+
ma?n mn 1 match
167+
man 1 match
168+
maaan No match (more than one a character)
169+
main No match (a is not followed by n)
170+
woman 1 match
171+
maon 1 match
172+
exmain 1 match
173+
'''
174+
175+
176+
# 8 - {} - Braces
177+
178+
'''
179+
Consider this code: {n,m}. This means at least n, and at most m repetitions of the pattern left to it.
180+
181+
Expression String Matched?
182+
a{2,3} abc dat No match
183+
abc daat 1 match (at daat)
184+
aabc daaat 2 matches (at aabc and daaat)
185+
aabc daaaat 2 matches (at aabc and daaaat)
186+
187+
Let's try one more example. This RegEx [0-9]{2, 4} matches at least 2 digits but not more than 4 digits
188+
189+
Expression String Matched?
190+
[0-9]{2,4} ab123csde 1 match (match at ab123csde)
191+
12 and 345673 3 matches (12, 3456, 73)
192+
1 and 2 No match
193+
'''
194+
195+
# 9. | - Alternation
196+
'''
197+
Vertical bar | is used for alternation (or operator).
198+
199+
Expression String Matched?
200+
a|b cde No match
201+
ade 1 match (match at ade)
202+
acdbea 3 matches (at acdbea)
203+
204+
Here, a|b match any string that contains either a or b
205+
'''
206+
# 10 () - Group
207+
'''
208+
Parentheses () is used to group sub-patterns. For example, (a|b|c)xz match any string that matches either a or b or c followed by xz
209+
210+
Expression String Matched?
211+
(a|b|c)xz ab xz No match
212+
abxz 1 match (match at abxz)
213+
axz cabxz 2 matches (at axzbc cabxz)
214+
'''
215+
216+
# 11. \ - Backslash
217+
'''
218+
Backlash \ is used to escape various characters including all metacharacters. For example,
219+
220+
\$a match if a string contains $ followed by a. Here, $ is not interpreted by a RegEx engine in a special way.
221+
222+
If you are unsure if a character has special meaning or not, you can put \ in front of it.
223+
This makes sure the character is not treated in a special way.
224+
225+
Special Sequences
226+
-------------------
227+
228+
Special sequences make commonly used patterns easier to write. Here's a list of special sequences:
229+
230+
\A - Matches if the specified characters are at the start of a string.
231+
232+
Expression String Matched?
233+
\A the the sun Match
234+
In the sun No match
235+
236+
\b - Matches if the specified characters are at the beginning or end of a word.
237+
238+
Expression String Matched?
239+
\bfoo football Match
240+
a football Match
241+
afootball No match
242+
243+
foo\b the foo Match
244+
the afoo test Match
245+
the afootest No match
246+
247+
\B - Opposite of \b. Matches if the specified characters are not at the beginning or end of a word.
248+
249+
Expression String Matched?
250+
\Bfoo football No match
251+
a football No match
252+
afootball Match
253+
254+
foo\B the foo No match
255+
the afoo test No match
256+
the afootest Match
257+
258+
\d - Matches any decimal digit. Equivalent to [0-9]
259+
260+
Expression String Matched?
261+
\d 12abc3 3 matches (at 12abc3)
262+
Python No match
263+
264+
\D - Matches any non-decimal digit. Equivalent to [^0-9]
265+
266+
Expression String Matched?
267+
\D 1ab34"50 3 matches (at 1ab34"50)
268+
1345 No match
269+
270+
\s - Matches where a string contains any whitespace character. Equivalent to [ \t\n\r\f\v].
271+
272+
Expression String Matched?
273+
\s Python RegEx 1 match
274+
PythonRegEx No match
275+
276+
\S - Matches where a string contains any non-whitespace character. Equivalent to [^ \t\n\r\f\v].
277+
278+
Expression String Matched?
279+
\S a b 2 matches (at a b)
280+
No match
281+
282+
\w - Matches any alphanumeric character (digits and alphabets). Equivalent to [a-zA-Z0-9_]. By the way, underscore _ is also considered an alphanumeric character.
283+
284+
Expression String Matched?
285+
\w 12&": ;c 3 matches (at 12&": ;c)
286+
%"> ! No match
287+
288+
289+
\W - Matches any non-alphanumeric character. Equivalent to [^a-zA-Z0-9_]
290+
291+
Expression String Matched?
292+
\W 1a2%c 1 match (at 1a2%c)
293+
Python No match
294+
295+
\Z - Matches if the specified characters are at the end of a string.
296+
297+
Expression String Matched?
298+
Python\Z I like Python 1 match
299+
I like Python Programming No match
300+
Python is fun. No match
301+
302+
Tip: To build and test regular expressions, you can use RegEx tester tools such as regex101. This tool not only helps you in creating regular expressions, but it also helps you learn it.
303+
304+
Now you understand the basics of RegEx, let's discuss how to use RegEx in your Python code.
305+
'''
306+
307+
308+
# From the above features we went through, here's the list of exercise for you!
309+
310+
# 1. Write a method(giveMeNumber) takes input as string, gives output as available numbers inside the give string.
311+
312+
# Sample,
313+
# givenInput = "hey my phone number starts with 91 as country code, then my 10 digit # continues - 9944294841"
314+
315+
# giveMeNumber(givenInput) #[91, 10, 9944294841]
316+
317+
318+
# 2.
319+
320+

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /