﻿ Python: Matches a string that has an a followed by zero or one 'b' - w3resource

# Python: Matches a string that has an a followed by zero or one 'b'

## Python Regular Expression: Exercise-4 with Solution

Write a Python program that matches a string that has an a followed by zero or one 'b'.

Sample Solution:-

Python Code:

``````import re
def text_match(text):
patterns = 'ab?'
if re.search(patterns,  text):
return 'Found a match!'
else:
return('Not matched!')

print(text_match("ab"))
print(text_match("abc"))
print(text_match("abbc"))
print(text_match("aabbc"))
```
```

Sample Output:

```Found a match!
Found a match!
Found a match!
Found a match!
```

Pictorial Presentation:

Flowchart:

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## Python: Tips of the Day

Getting the last element of a list:

some_list[-1] is the shortest and most Pythonic.

In fact, you can do much more with this syntax. The some_list[-n] syntax gets the nth-to-last element. So some_list[-1] gets the last element, some_list[-2] gets the second to last, etc, all the way down to some_list[-len(some_list)], which gives you the first element.

You can also set list elements in this way. For instance:

```>>> some_list = [1, 2, 3]
>>> some_list[-1] = 5 # Set the last element
>>> some_list[-2] = 3 # Set the second to last element
>>> some_list
[1, 3, 5]
```

Note that getting a list item by index will raise an IndexError if the expected item doesn't exist. This means that some_list[-1] will raise an exception if some_list is empty, because an empty list can't have a last element.

Ref: https://bit.ly/3d8TfFP