Multiple spaces
Input
split_and_join(' Hello world ')
Output
Hello world
Splitting removes extra whitespace, joining with default single space gives 'Hello world'.
Full lesson preview
Split a sentence into words and join them
Split a sentence on whitespace into words and rejoin them with a given delimiter.
Python practice8 minString PatternsBeginnerLast updated March 18, 2026
Problem statement
Implement split_and_join(sentence, delimiter=' ') which splits sentence into words using whitespace (any sequence of spaces, tabs, newlines, etc.) and then joins those words using the provided delimiter. Leading/trailing whitespace should be removed. If the sentence has no words, return an empty string.
Task
Practice splitting on arbitrary whitespace and joining tokens, producing predictable normalized joins.
Examples
Custom delimiter
Input
split_and_join('one\ttwo\nthree', ',')
Output
one,two,three
Tabs/newlines are treated as separators; join with comma.
Input format
A call to split_and_join(sentence, delimiter) where sentence is a string and delimiter is an optional string.
Output format
A single string returned: words joined by the delimiter, or empty string if no words.
Constraints
Do not use external libraries. Use Python string methods. Preserve word contents (do not remove punctuation).
Samples
Sample 1
Input
split_and_join(' a b c ')
Output
a b c
Extra spaces collapsed and words joined with a single space.