Python String and List Operations with Practical Code Examples

The article introduces several useful Python techniques for handling strings and lists, starting with common string operations such as reversing a string, checking for palindromes, extracting unique characters, and comparing element composition.

String reversal examples:

# Method 1
s = 'hello  world'
print(s[::-1])

# Method 2
from functools import reduce
print(reduce(lambda x,y: y+x, s))

Palindrome check example (note the syntax error in the original source is corrected):

s1 = 'abccba'
s2 = 'abcde'

def func(s):
    if s == s[::-1]:
        print('回文')
    else:
        print('不回文')

func(s1)
func(s2)

Finding unique characters using a set and joining them back into a string, as well as deduplicating a list:

# String unique characters
s1 = 'wwweeerftttg'
print(''.join(set(s1)))  # e.g., 'ftgwer'

# List deduplication
l1 = [2, 4, 5, 6, 7, 1, 2]
print(list(set(l1)))  # [1, 2, 4, 5, 6, 7]

Checking whether two strings contain the same multiset of characters using collections.Counter :

from collections import Counter
s1, s2, s3 = 'asdf', 'fdsa', 'sfad'
c1, c2, c3 = Counter(s1), Counter(s2), Counter(s3)
if c1 == c2 and c2 == c3:
    print('符合')

The article then moves to list operations, showing how to flatten nested lists with iteration_utilities.deepflatten , unpack an iterable with the starred expression, and retrieve the largest or smallest N elements using heapq :

from iteration_utilities import deepflatten
l = [[12, 5, 3], [2.4, [5], [6, 9, 7]]]
print(list(deepflatten(l)))

first, *middle, last = grades  # *expression splits an iterable

import heapq
nums = [1, 8, 2, 23, 7, -4, 18, 23, 42, 37, 2]
print(heapq.nlargest(3, nums))   # [42, 37, 23]
print(heapq.nsmallest(3, nums))  # [-4, 1, 2]

portfolio = [
    {'name': 'IBM', 'shares': 100, 'price': 91.1},
    {'name': 'AAPL', 'shares': 50, 'price': 543.22},
    {'name': 'FB', 'shares': 200, 'price': 21.09},
    {'name': 'HPQ', 'shares': 35, 'price': 31.75},
    {'name': 'YHOO', 'shares': 45, 'price': 16.35},
    {'name': 'ACME', 'shares': 75, 'price': 115.65}
]
cheap = heapq.nsmallest(3, portfolio, key=lambda s: s['price'])

Additional practical snippets demonstrate how to check an object's memory footprint with sys.getsizeof , use print with custom separators and end characters, and perform reading and writing of plain and compressed files (gzip, bz2):

import sys
s1 = 'a'
s2 = 'aaddf'
n1 = 32
print(sys.getsizeof(s1))  # 50
print(sys.getsizeof(s2))  # 54
print(sys.getsizeof(n1))  # 28

# Print to file
with open('somefile.txt', 'rt') as f:
    print('Hello World!', file=f)

# Custom separator and end
print('GKY', 1995, 5, 18, sep='-', end='!!\n')  # GKY-1995-5-18!!

# Read gzip file
import gzip
with open('somefile.gz', 'rt') as f:
    text = f.read()

# Write gzip file
with open('somefile.gz', 'wt') as f:
    f.write(text)

# Read bz2 file
import bz2
with open('somefile.bz2', 'rt') as f:
    text = f.read()

Overall, the collection serves as a quick‑reference guide for Python beginners and intermediate developers to perform everyday data manipulation and I/O tasks efficiently.