範本方法

Python 中的正規表示法

Maria Eugenia Inzaugarat

Data Scientist

Template 字串

語法更簡單
比 f-strings 慢
受限：不支援格式規格
適合處理外部已格式化的字串

基本語法

from string import Template

my_string = Template('Data science has been called $identifier')

my_string.substitute(identifier="sexiest job of the 21st century")

'Data science has been called sexiest job of the 21st century'

替換

可使用多個 $identifier
可搭配變數

from string import Template
job = "Data science"
name = "sexiest job of the 21st century"

my_string = Template('$title has been called $description')

my_string.substitute(title=job, description=name)

'Data science has been called sexiest job of the 21st century'

替換

後面接合法字元時，用 ${identifier}

my_string = Template('I find Python very ${noun}ing but my sister has lost $noun')

my_string.substitute(noun="interest")

'I find Python very interesting but my sister has lost interest'

替換

使用 $$ 跳脫美元符號

my_string = Template('I paid for the Python course only $$ $price, amazing!')

my_string.substitute(price="12.50")

'I paid for the Python course only $ 12.50, amazing!'

替換

缺少佔位符時會拋出錯誤

favorite = dict(flavor="chocolate")

my_string = Template('I love $flavor $cake very much')

my_string.substitute(favorite)

Traceback (most recent call last):
KeyError: 'cake'

替換

favorite = dict(flavor="chocolate")
my_string = Template('I love $flavor $cake very much')

try:
    my_string.substitute(favorite) 
except KeyError:
      print("missing information")

missing information

安全替換

盡量回傳可用字串
缺少的佔位符會保留在結果中

favorite = dict(flavor="chocolate")
my_string = Template('I love $flavor $cake very much')

my_string.safe_substitute(favorite)

'I love chocolate $cake very much'

該用哪一種？

str.format()：
- 入門佳選，觀念可沿用到 f-strings。
- 相容所有 Python 版本。
f-strings：
- 通常最建議使用的方法。
- 僅適用於較新的 Python 版本（3.6+）。
Template 字串：
- 處理外部或使用者提供的字串時使用

一起來練習吧！

Python 中的正規表示法