Splitting Strings with Multiple Delimiters

Problem: Split a string containing various delimiters into tokens. For example: s = 'ab;cd|efg|hi,jkl|mn\topq;rst,uvw\txyz' where delimiters include ;, |, ,, and \t.

Approaches:

1. Apply str.split() iteratively for each delimiter.
2. Use re.split() with a regular expression for single-pass splitting.

Iterative Splitting with str.split():

def split_multiple(s, delimiters):
    tokens = [s]
    for d in delimiters:
        temp = []
        for segment in tokens:
            temp.extend(segment.split(d))
        tokens = temp
    return [token for token in tokens if token]

s = "ab;cd|efg|hi,jkl|mn\topq;rst,uvw\txyz"
print(split_multiple(s, ",;|\t"))

Single-Pass Splitting with re.split():

import re

s = "ab;cd|efg|hi,jkl|mn\topq;rst,uvw\txyz"
print(re.split(r'[,;|\t]+', s))

Checking String Start or End

Problem: Add executable permissions to files ending with .sh or .py in a directory.

Solution: Use str.endswith() with a tuple of suffixes.

filenames = ["a.c", "b.sh", "d.py", "e.java"]
for name in filenames:
    if name.endswith((".sh", ".py")):
        # Add executable permissions
        pass

Reformatting Date Strings

Problem: Convert date strings from yyyy-mm-dd to mm/dd/yyyy.

Solution: Use re.sub() with capture groups to reorder components.

import re

log = "2016-05-21 10:39:26 status unpacked python3-pip:all 2016-05-23 10:49:26 status half-configured python3"
result = re.sub(r'(\d{4})-(\d{2})-(\d{2})', r'\2/\3/\1', log)
print(result)

Joining Multiple Strings

Problem: Efficiently concatenate a list of strings.

Solution:

1. Iterative concatenation with + (inefficient for large lists).
2. Use str.join() for optimal performance.

parts = ["<0112>", "<32>", "<1024x768>", "<60>", "<1>", "<100.0>", "<500.0>"]
print(''.join(parts))

Aligning Strings

Problem: Align text to left, right, or center within fixed-width fields.

Solution:

• Use str.ljust(), str.rjust(), str.center().
• Use formatting with format() or f-strings.

data = {"a": 100, "as": 0.01, "wer": 500.0, "cc": 12}
max_key_len = max(len(key) for key in data)

for key, value in data.items():
    print(f"{key.ljust(max_key_len)} : {value}")

Removing Unwanted Characters

Problem: Strip extraneous characters (whitespace, control characters, diacritics).

Techniques:

1. Trimming: strip(), lstrip(), rstrip().
2. Slicing: Remove fixed-position characters.
3. Replacement: replace() or re.sub().
4. Translation: str.translate() with a mapping table.

Examples:

# Trim whitespace
s = "  abc  123   "
print(s.strip())

# Remove specific characters
s = "+++abc---"
print(s.strip('+-'))

# Replace control characters
s = "\tabc\t123\txyz\ropt\r"
print(re.sub(r'[\t\r]', '', s))

# Translate characters
s = "abc123def456xyz"
trans_table = str.maketrans("abcxyz", "xyzabc")
print(s.translate(trans_table))

# Remove diacritics
import unicodedata

def remove_accents(s):
    nfkd_form = unicodedata.normalize('NFKD', s)
    return ''.join(c for c in nfkd_form if not unicodedata.combining(c))

s = "āáǎà ōóǒò ēéěè īíǐì"
print(remove_accents(s))