Longest run of a repeated character

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Python Practice › String Programs › Program 8

Longest run of a repeated character

MediumString Programs · 8 of 106

Write a Python program to find the character that repeats most times in a row (consecutively) in a string.

Input
"aabbbbcccdd"
Output
b 4

Approach

  1. Walk through the string, counting the current run, and remember the longest one.

Solution

Python
text = "aabbbbcccdd"best_char, best_len = text[0], 1run_len = 1for i in range(1, len(text)):    if text[i] == text[i - 1]:        run_len += 1    else:        run_len = 1    if run_len > best_len:        best_char, best_len = text[i], run_lenprint(best_char, best_len)
Output
b 4

Line by line

Lines 5-8

The run grows while characters repeat and resets on a change.

Lines 9-10

Save the run if it is the longest so far.

Tip

itertools.groupby(text) groups consecutive equal characters for you.

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Least frequent character

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Python Practice › String Programs › Program 45

Least frequent character

EasyString Programs · 45 of 106

Write a Python program to find the least frequent character in a string.

Input
"abcdabdggfhf"
Output
c Counter({'a': 2, 'b': 2, 'd': 2, 'g': 2, 'f': 2, 'c': 1, 'h': 1})

Approach

  1. Count characters and take the one with the smallest count.

Solution

Python
from collections import Counter text = "abcdabdggfhf"counts = Counter(text)print(min(counts, key=counts.get), counts)
Output
c Counter({'a': 2, 'b': 2, 'd': 2, 'g': 2, 'f': 2, 'c': 1, 'h': 1})

Line by line

Line 5

key=counts.get compares characters by their counts; with ties, the first seen wins.

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Count occurrences of a word

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Python Practice › String Programs › Program 44

Count occurrences of a word

EasyString Programs · 44 of 106

Write a Python program to count how many times a whole word occurs in a string.

Input
"food" in "I want to eat fast food"; "are" in "We are learning Python, wow are you"
Output
1
2

Approach

  1. Split into words, strip punctuation, count matches.

Solution

Python
def count_word(text, word):    return sum(1 for w in text.split() if w.strip(",.!?") == word) print(count_word("I want to eat fast food", "food"))print(count_word("We are learning Python, wow are you", "are"))
Output
1
2

Line by line

Line 2

Counting whole words avoids matching “are” inside “hare”.

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Position of a word in a sentence

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Python Practice › String Programs › Program 43

Position of a word in a sentence

EasyString Programs · 43 of 106

Write a Python program to find the position (word number, starting at 1) of a word in a sentence.

Input
word = "problems", text = "I am solving problems based on strings"
Output
word number: 4
character index: 13

Approach

  1. Split into words and use index(); add 1 for a human-friendly position.

Solution

Python
text = "I am solving problems based on strings"word = "problems"words = text.split()print("word number:", words.index(word) + 1)print("character index:", text.find(word))
Output
word number: 4
character index: 13

Line by line

Line 4

List indexes start at 0, so add 1.

Line 5

find() gives the character position instead.

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Number words to digits

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Python Practice › String Programs › Program 42

Number words to digits

EasyString Programs · 42 of 106

Write a Python program to convert number words into a number.

Input
"five four three two one"
Output
54321

Approach

  1. Map each word to its digit and join.

Solution

Python
words = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]text = "five four three two one"digits = "".join(str(words.index(w)) for w in text.split())print(int(digits))
Output
54321

Line by line

Line 4

words.index(w) is the digit for each word.

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Float to 3 decimal places as a string

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Python Practice › String Programs › Program 41

Float to 3 decimal places as a string

EasyString Programs · 41 of 106

Write a Python program to format a float to 3 decimal places and convert it to a string.

Input
2.14652
Output
2.147 str

Approach

  1. Use the format spec .3f.

Solution

Python
x = 2.14652text = f"{x:.3f}"print(text, type(text).__name__)
Output
2.147 str
Note

Formatting rounds, so 2.14652 becomes “2.147”, not “2.146” as the original sample showed. Use str(int(x * 1000) / 1000) if you need to cut off digits instead.

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Split and join a string

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Python Practice › String Programs › Program 40

Split and join a string

EasyString Programs · 40 of 106

Write a Python program to split a string into words and join them with “-“.

Input
"Hello world"
Output
['Hello', 'world']
Hello-world

Approach

  1. split() then "-".join().

Solution

Python
parts = "Hello world".split()print(parts)print("-".join(parts))
Output
['Hello', 'world']
Hello-world

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Remove newlines from a string

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Python Practice › String Programs › Program 39

Remove newlines from a string

EasyString Programs · 39 of 106

Write a Python program to remove newline characters from a string.

Input
"objectoriented\nprogramming\n"
Output
'objectoriented\nprogramming'
'objectorientedprogramming'

Approach

  1. strip() for the ends, replace("\n", "") for everywhere.

Solution

Python
text = "objectoriented\nprogramming\n"print(repr(text.rstrip("\n")))print(repr(text.replace("\n", "")))
Output
'objectoriented\nprogramming'
'objectorientedprogramming'

Line by line

Line 2

rstrip("\n") removes only trailing newlines.

Line 3

replace removes them everywhere.

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Convert to uppercase

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Python Practice › String Programs › Program 38

Convert to uppercase

EasyString Programs · 38 of 106

Write a Python program to convert all the characters in a string to uppercase.

Input
"I live in pune"
Output
I LIVE IN PUNE

Approach

  1. Use upper().

Solution

Python
print("I live in pune".upper())
Output
I LIVE IN PUNE

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Swap the first and last letters of a string

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Python Practice › String Programs › Program 37

Swap the first and last letters of a string

EasyString Programs · 37 of 106

Write a Python program to exchange the first and last letters of a string.

Input
"We are learning python"
Output
ne are learning pythoW

Approach

  1. last + middle + first.

Solution

Python
text = "We are learning python"print(text[-1] + text[1:-1] + text[0])
Output
ne are learning pythoW

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