S2Q2 · Replace Consonants with Hash

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Type: Full I/O -multiline string processing

Core idea: for each character, if it's an alphabetic consonant replace with #, otherwise keep it.

n = int(input())
vowels = "aeiouAEIOU"
for _ in range(n):
    line = input()
    print("".join("#" if c.isalpha() and c not in vowels else c for c in line))

Key rules: - Only alphabetic characters (isalpha()) can be consonants - Vowels (aeiouAEIOU) stay unchanged - Non-alphabetic characters (spaces, punctuation) stay unchanged - Process and print line by line -no need to buffer all lines

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Problem Statement

Problem (I/O type)

Read n lines. Replace every consonant with #. Vowels and non-alphabetic characters stay unchanged.

Example:

Input

2
Hello World
Good Night

Output

#e##o #o###
#oo# #i###

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Understanding the problem

For each character, three cases:

Character type	Action
Vowel (a e i o u, upper or lower)	Keep unchanged
Consonant (alphabetic, not a vowel)	Replace with #
Non-alphabetic (space, digit, punctuation)	Keep unchanged

Tracing "Hello World":

Char	isalpha()	Vowel?	Output
H	✅	❌	#
e	✅	✅	e
l	✅	❌	#
l	✅	❌	#
o	✅	✅	o
	❌	-
W	✅	❌	#
o	✅	✅	o
r	✅	❌	#
l	✅	❌	#
d	✅	❌	#

Result: #e##o #o###

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Solution approaches

Pythonic (generator + join)Explanatory (loop)Using str.translate()Using lambda + map

n = int(input())
vowels = "aeiouAEIOU"
for _ in range(n):
    line = input()
    print("".join("#" if c.isalpha() and c not in vowels else c for c in line))

Process each line as it's read. The generator expression handles all three cases in one ternary.

n = int(input())
vowels = "aeiouAEIOU"
for _ in range(n):
    line = input()
    result = ""
    for c in line:
        if c.isalpha() and c not in vowels:
            result += "#"
        else:
            result += c
    print(result)

Explicit loop -each condition step visible.

import string

n = int(input())
vowels = "aeiouAEIOU"
consonants = "".join(c for c in string.ascii_letters if c not in vowels)
table = str.maketrans(consonants, "#" * len(consonants))

for _ in range(n):
    print(input().translate(table))

Build a translation table mapping every consonant to #. str.translate() applies it in one pass -no per-character checking in Python code.

n = int(input())
vowels = "aeiouAEIOU"
replace = lambda c: "#" if c.isalpha() and c not in vowels else c
for _ in range(n):
    print("".join(map(replace, input())))

map(replace, line) applies the lambda to every character. "".join(...) reassembles. Clean functional pipeline.

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Key takeaways

01

isalpha() + not in vowels = consonant

Two conditions together identify a consonant: the character must be alphabetic AND not a vowel. Spaces, digits, and punctuation fail isalpha() and are kept unchanged automatically.

02

Process line by line -no buffering needed

Unlike problems that need the full input before processing, this one can print each line immediately after reading it. No need to store all lines in a list.

03

str.translate() for character-level substitution

When replacing a fixed set of characters, str.maketrans() + str.translate() is the most efficient approach -it's a single O(n) pass with a lookup table, no Python-level loop.