Python字符串len()、split()、join()深度解析

text = "Hello\n世界！🚀"
print(len(text))  # 输出：9（H e l l o \n 世 界 ！🚀）

line = "Name,Age,City\nAlice,30,New York"
headers, data = line.split('\n')
columns = headers.split(',')

log = "[ERROR] File not found: data.txt"
level, message = log.split(']', 1)[1].split(':', 1)

ids = [1, 2, 3]
query = "SELECT * FROM users WHERE id IN (" + ",".join(map(str, ids)) + ")"
# 输出：SELECT * FROM users WHERE id IN (1,2,3)

items = ["Apple", "Banana", "Cherry"]
html = "<ul>\n" + "\n".join([f"<li>{item}</li>" for item in items]) + "\n</ul>"

header = b"\x01\x02\x03"
payload = b"DATA"
packet = header + b"\x00".join([header, payload])

log_entry = "127.0.0.1 - - [10/Oct/2023:13:55:36 +0000] \"GET / HTTP/1.1\" 200 2326"
 
# 分割关键字段
parts = log_entry.split()
ip, timestamp, request = parts[0], parts[3][1:-1], parts[5]
 
# 重建结构化数据
cleaned = f"{ip} | {timestamp} | {request}"

args = "--input data.csv --output result.json --verbose"
 
# 分割参数
params = args.split('--')[1:]
 
# 构建字典
config = {}
for param in params:
    key, value = param.split(maxsplit=1)
    config[key.strip()] = value.strip() if value else True

sentence = "自然语言处理是人工智能的重要领域。"
 
# 分词处理
words = sentence.split()
 
# 去除停用词
stopwords = {"是", "的"}
filtered = [word for word in words if word not in stopwords]
 
# 重建句子
processed = " ".join(filtered)

# 错误：join()参数必须为字符串可迭代对象
''.join(123)  # TypeError
 
# 解决：显式转换类型
''.join(map(str, [1, 2, 3]))

# 错误：split()可能产生空字符串
"".split(',')  # 返回['']
 
# 解决：过滤空值
[x for x in text.split(',') if x]

# 错误：混合字节串和字符串
b'data'.join(['a', 'b'])  # TypeError
 
# 解决：统一类型
''.join([s.decode() for s in byte_list])

# 低效方式
result = ""
for s in list:
    result += s
 
# 高效方式
result = ''.join(list)

# 内存友好型处理大文件
with open('bigfile.txt') as f:
    chunks = (f.read(1024) for _ in range(100))
    content = ''.join(chunks)

from concurrent.futures import ThreadPoolExecutor
 
def process_chunk(chunk):
    return chunk.upper()
 
with ThreadPoolExecutor() as executor:
    processed = list(executor.map(process_chunk, big_list))
 
final = ''.join(processed)