Python split() 字串分割

split() 方法用來將字串依據指定的分隔符號分割成 list。

基本用法

text = "apple,banana,orange"
result = text.split(",")
print(result)  # ['apple', 'banana', 'orange']

語法

str.split(sep=None, maxsplit=-1)

• sep：分隔符號，預設為 None（空白字元）
• maxsplit：最大分割次數，-1 表示無限制

使用空白分割（預設）

當不指定分隔符號時，會以任意空白字元分割，並自動忽略多餘的空白：

text = "Hello   World   Python"
result = text.split()
print(result)  # ['Hello', 'World', 'Python']

# 包含換行和 Tab
text = "Hello\nWorld\tPython"
result = text.split()
print(result)  # ['Hello', 'World', 'Python']

指定分隔符號

# 逗號分隔
text = "a,b,c,d"
print(text.split(","))  # ['a', 'b', 'c', 'd']

# 冒號分隔
text = "name:Alice:age:25"
print(text.split(":"))  # ['name', 'Alice', 'age', '25']

# 多字元分隔符號
text = "apple--banana--orange"
print(text.split("--"))  # ['apple', 'banana', 'orange']

maxsplit 參數

限制分割次數：

text = "a,b,c,d,e"

print(text.split(",", 1))   # ['a', 'b,c,d,e']
print(text.split(",", 2))   # ['a', 'b', 'c,d,e']
print(text.split(",", 3))   # ['a', 'b', 'c', 'd,e']

處理空字串

# 連續分隔符號會產生空字串
text = "a,,b,,c"
print(text.split(","))  # ['a', '', 'b', '', 'c']

# 使用 filter 過濾空字串
result = list(filter(None, text.split(",")))
print(result)  # ['a', 'b', 'c']

# 或使用 list comprehension
result = [x for x in text.split(",") if x]
print(result)  # ['a', 'b', 'c']

splitlines() - 按行分割

text = """Line 1
Line 2
Line 3"""

lines = text.splitlines()
print(lines)  # ['Line 1', 'Line 2', 'Line 3']

# 保留換行符號
lines = text.splitlines(keepends=True)
print(lines)  # ['Line 1\n', 'Line 2\n', 'Line 3']

rsplit() - 從右邊開始分割

text = "a,b,c,d,e"

print(text.rsplit(",", 1))   # ['a,b,c,d', 'e']
print(text.rsplit(",", 2))   # ['a,b,c', 'd', 'e']

實際範例

解析 CSV 資料

csv_line = "Alice,25,Taipei,Engineer"
fields = csv_line.split(",")
name, age, city, job = fields
print(f"{name} is a {age}-year-old {job} from {city}")

解析 URL 路徑

url = "https://example.com/users/123/profile"
parts = url.split("/")
print(parts)  # ['https:', '', 'example.com', 'users', '123', 'profile']

# 取得 user_id
user_id = url.split("/")[-2]
print(user_id)  # 123

解析 key=value 格式

config = "host=localhost;port=5432;database=mydb"

settings = {}
for item in config.split(";"):
    key, value = item.split("=")
    settings[key] = value

print(settings)  # {'host': 'localhost', 'port': '5432', 'database': 'mydb'}

處理使用者輸入

# 一次讀取多個數字
user_input = "10 20 30 40 50"
numbers = [int(x) for x in user_input.split()]
print(numbers)  # [10, 20, 30, 40, 50]
print(sum(numbers))  # 150

取得檔案名稱和副檔名

filename = "document.backup.txt"

# 使用 rsplit 限制分割一次
name, ext = filename.rsplit(".", 1)
print(f"Name: {name}, Extension: {ext}")
# Name: document.backup, Extension: txt

搭配 join() 使用

split() 和 join() 經常搭配使用：

text = "hello world python"

# 分割後重新組合
words = text.split()
result = "-".join(words)
print(result)  # hello-world-python

# 移除多餘空白
text = "  hello    world   python  "
result = " ".join(text.split())
print(result)  # hello world python

注意事項

# split() 和 split(" ") 的差異
text = "hello  world"

print(text.split())      # ['hello', 'world']（忽略多餘空白）
print(text.split(" "))   # ['hello', '', 'world']（保留空字串）