Python replace() 字串取代
replace() 方法用來將字串中的指定子字串替換成另一個字串。
基本用法
text = "Hello World"
result = text.replace("World", "Python")
print(result) # Hello Python
語法
str.replace(old, new, count=-1)
old：要被替換的子字串new：替換後的字串count：最大替換次數，-1 表示全部替換（預設）
替換所有出現的子字串
text = "apple apple apple"
result = text.replace("apple", "orange")
print(result) # orange orange orange
限制替換次數
text = "apple apple apple apple"
print(text.replace("apple", "orange", 1)) # orange apple apple apple
print(text.replace("apple", "orange", 2)) # orange orange apple apple
print(text.replace("apple", "orange", 3)) # orange orange orange apple
刪除子字串
將子字串替換為空字串：
text = "Hello, World!"
result = text.replace(",", "")
print(result) # Hello World!
# 移除所有空格
text = "Hello World Python"
result = text.replace(" ", "")
print(result) # HelloWorldPython
字串是不可變的
replace() 會回傳新的字串，原字串不會被修改：
text = "Hello World"
result = text.replace("World", "Python")
print(text) # Hello World（原字串不變）
print(result) # Hello Python
大小寫敏感
replace() 是大小寫敏感的：
text = "Hello hello HELLO"
result = text.replace("hello", "hi")
print(result) # Hello hi HELLO
不區分大小寫的替換
import re
text = "Hello hello HELLO"
result = re.sub("hello", "hi", text, flags=re.IGNORECASE)
print(result) # hi hi hi
鏈式呼叫
可以連續呼叫多個 replace()：
text = "Hello, World!"
result = text.replace("Hello", "Hi").replace("World", "Python").replace("!", "?")
print(result) # Hi, Python?
實際範例
清理資料
# 移除特殊字元
text = "Hello! How are you? I'm fine."
clean = text.replace("!", "").replace("?", "").replace("'", "")
print(clean) # Hello How are you Im fine.
# 統一換行符號
text = "Line1\r\nLine2\rLine3\nLine4"
result = text.replace("\r\n", "\n").replace("\r", "\n")
print(result.split("\n")) # ['Line1', 'Line2', 'Line3', 'Line4']
格式化電話號碼
phone = "0912-345-678"
clean_phone = phone.replace("-", "")
print(clean_phone) # 0912345678
# 反過來格式化
phone = "0912345678"
formatted = f"{phone[:4]}-{phone[4:7]}-{phone[7:]}"
print(formatted) # 0912-345-678
模板替換
template = "Dear {name}, your order #{order_id} has been shipped."
message = template.replace("{name}", "Alice").replace("{order_id}", "12345")
print(message) # Dear Alice, your order #12345 has been shipped.
處理 HTML 特殊字元
def escape_html(text):
return (text
.replace("&", "&")
.replace("<", "<")
.replace(">", ">")
.replace('"', """)
.replace("'", "'"))
html = '<script>alert("XSS")</script>'
safe = escape_html(html)
print(safe) # <script>alert("XSS")</script>
使用字典進行多重替換
def multi_replace(text, replacements):
for old, new in replacements.items():
text = text.replace(old, new)
return text
text = "I love apples and bananas"
replacements = {
"apples": "oranges",
"bananas": "grapes"
}
result = multi_replace(text, replacements)
print(result) # I love oranges and grapes
translate() 方法
對於單字元替換，translate() 效率更高：
# 建立轉換表
table = str.maketrans("aeiou", "12345")
text = "hello world"
result = text.translate(table)
print(result) # h2ll4 w4rld
# 刪除字元
table = str.maketrans("", "", "aeiou")
result = text.translate(table)
print(result) # hll wrld
使用正規表達式
對於複雜的替換需求，可以使用 re.sub()：
import re
# 替換多個空格為單一空格
text = "Hello World Python"
result = re.sub(r"\s+", " ", text)
print(result) # Hello World Python
# 替換數字
text = "Order 123 and Order 456"
result = re.sub(r"\d+", "XXX", text)
print(result) # Order XXX and Order XXX