[Tut] Python | Split String into List of Substrings

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[Tut] Python | Split String into List of Substrings - xSicKxBot - 12-11-2022

Python | Split String into List of Substrings

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Summary: Use Python’s built-in split function to

Code:
split

a given string into a list substrings. Other methods include using the

Code:
regex

library and the

Code:
map

function.

[b]Minimal Example[/b]

Code:
text = "Python Java Golang" # Method 1
print(text.split()) # Method 2
import re
print(re.split('\s+',text)) # Method 2.1
print(re.findall('\S+', text)) # Method 3
li = list(map(str.strip, text.split()))
res = []
for i in li: for j in i.split(): res.append(j)
print(res) # OUTPUTS: ['Python', 'Java', 'Golang']

Problem Formulation

Problem: Given a string containing numerous substrings. How will you split the string into a list of substrings?

Let’s understand the problem with the help of an example.

[b]Example[/b]

Code:
# Input
text = "word1 word2 word3 word4 word5" # Output
['word1', 'word2', 'word3', 'word4', 'word5']

[b]Method 1: Using strip[/b]

Approach: Use the

Code:
split("sep")

function where sep is the specified separator. In our case the separator is a space. Hence, you do not need to pass any separator to the function as whitespaces are considered to be default separators for the

Code:
split

function. Therefore, whenever a space occurs the string will be split and the substring will be stored in a list.

Code:

Code:
text = "word1 word2 word3 word4 word5"
print(text.split()) # ['word1', 'word2', 'word3', 'word4', 'word5']

[b]Method 2: Using re.split[/b]

The

Code:
re.split(pattern, string)

method matches all occurrences of the

Code:
pattern

in the

Code:
string

and divides the string along the matches resulting in a list of strings between the matches. For example,

Code:
re.split('a', 'bbabbbab')

results in the list of strings

Code:
['bb', 'bbb', 'b']

.

Approach: Use thr

Code:
re.split('\s+',text)

method, where

Code:
text

is the given string and ‘

Code:
\s+

‘ returns a match whenever it finds a space in the string.Therefore, on every occurrence of a space the string will be split.

Code:

Code:
import re text = "word1 word2 word3 word4 word5"
print(re.split('\s+',text)) # ['word1', 'word2', 'word3', 'word4', 'word5']

Related Read: Python Regex Split

[b]Method 3: Using re.findall[/b]

The

Code:
re.findall(pattern, string)

method scans

Code:
string

from left to right, searching for all non-overlapping matches of the

Code:
pattern

. It returns a list of strings in the matching order when scanning the string from left to right.

Related Read: Python re.findall() – Everything You Need to Know

Approach: Use thr

Code:
re.findall('\S+',text)

method, where

Code:
text

is the given string and ‘

Code:
\S+

‘ returns a match whenever it finds a normal character in the string except whitespace. Therefore, all the non-whitespace characters will be grouped together until the script encounters a space. On the occurrence of a space, the string will be split and the next group of characters that do not include a space will be searched.

Code:

Code:
import re text = "word1 word2 word3 word4 word5"
print(re.findall('\S+', text)) # ['word1', 'word2', 'word3', 'word4', 'word5']

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[b]Method 4: Using map[/b]

Prerequisite: The

Code:
map()

function transforms one or more iterables into a new one by applying a “transformator function” to the i-th elements of each iterable. The arguments are the transformator function object and one or more iterables. If you pass n iterables as arguments, the transformator function must be an n-ary function taking n input arguments. The return value is an iterable map object of transformed, and possibly aggregated, elements.

Related Read: Python map() — Finally Mastering the Python Map Function [+Video]

Approach: Use the

Code:
map

function such that the iterable is the split list of substrings. This is the second argument of the map method. Now each item of this list will be passed to the

Code:
strip

method which eliminates the trailing spaces if any and then returns a map object containing the split substrings. You can convert this map object to a list using the list constructor.

Code:

Code:
text = "word1 word2 word3 word4 word5"
li = list(map(str.strip, text.split()))
res = []
for i in li: for j in i.split(): res.append(j)
print(res) # ['word1', 'word2', 'word3', 'word4', 'word5']

Exercise

Problem: Given a string containing numerous substrings separated by commas and spaces. How will you extract the substrings and store them in a list? Note that you have to eliminate the whitespaces as well as the commas.

Code:
# Input
text = "One, Two, Three"
# Output
['One', 'Two', 'Three']

Hint: Python | Split String by Comma and Whitespace

Solution:

Code:
text = "One, Two, Three"
print([x.strip() for x in text.split(',')])
# ['One', 'Two', 'Three']

Conclusion

With that, we come to the end of this tutorial. I hope the methods discussed in this article have helped you and answered your queries. Please stay tuned and subscribe for more solutions and discussions in the future.

Happy learning!

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