假如有個任務(wù)： 給定一個字符串，通過查詢字典，來替換給定字符中的變量。如果使用通常的方法：
>>> "This is a %(var)s" % {"var":"dog"}'This is a dog'>>>其實可以使用string.Template類來實現(xiàn)上面的替換
>>> from string import Template>>> words = Template("This is $var")>>> print(words.substitute({"var": "dog"})) # 通過字典的方式來傳參This is dog>>> print(words.substitute(var="dog")) # 通過關(guān)鍵字方式來傳參This is dog>>>在創(chuàng)建Template實例時，在字符串格式中，可以使用兩個美元符來代替$，還可以用${}將 變量擴起來，這樣的話，變量后面還可以接其他字符或數(shù)字，這個使用方式很像Shell或者Perl里面的語言。下面以letter模板來示例一下:
>>> from string import Template>>> letter = """Dear $customer,... I hope you are having a great time!... If you do not find Room $room to your satisfaction, let us know.... Please accept this $$5 coupon.... Sincerely,... $manager,... ${name}Inn""">>> template = Template(letter)>>> letter_dict = {"name": "Sleepy", "customer": "Fred Smith", "manager": "Tom Smith", "room": 308}>>> print(template.substitute(letter_dict))Dear Fred Smith,I hope you are having a great time!If you do not find Room 308 to your satisfaction, let us know.Please accept this $5 coupon. Sincerely, Tom Smith, SleepyInn>>>有時候，為了給substitute準(zhǔn)備一個字典做參數(shù)，最簡單的方法是設(shè)定一些本地變量，然后將這些變量交給local()(此函數(shù)創(chuàng)建一個字典，字典中的key就是本地變量，本地變量的值通過key來訪問)。
>>> locals() # 剛進入時，沒有其他變量{'__builtins__': <module '__builtin__' (built-in)>, '__name__': '__main__', '__doc__': None, '__package__': None}>>> name = "Alice" # 創(chuàng)建本地變量name >>> age = 18 # 創(chuàng)建本地變量age>>> locals() # 再執(zhí)行l(wèi)ocals()函數(shù)就可以看到name, age的鍵值隊{'name': 'Alice', '__builtins__': <module '__builtin__' (built-in)>, 'age': 18, '__package__': None, '__name__': '__mai__', '__doc__': None}>>> locals()["name"] # 通過鍵name來獲取值'Alice'>>> locals()["age"] # 通過鍵age來獲取值18>>>有了上面的例子打底來看一個示例：
>>> from string import Template>>> msg = Template("The square of $number is $square")>>> for number in range(10):... square = number * number... print msg.substitute(locals())...The square of 0 is 0The square of 1 is 1The square of 2 is 4The square of 3 is 9另外一種方法是使用關(guān)鍵字參數(shù)語法而非字典，直接將值傳遞給substitute。
>>> from string import Template>>> msg = Template("The square of $number is $square")>>> for i in range(4):... print msg.substitute(number=i, square=i*i)...The square of 0 is 0The square of 1 is 1The square of 2 is 4The square of 3 is 9>>>甚至可以同時傳遞字典和關(guān)鍵字
>>> from string import Template>>> msg = Template("The square of $number is $square")>>> for number in range(4):... print msg.substitute(locals(), square=number*number)...The square of 0 is 0The square of 1 is 1The square of 2 is 4The square of 3 is 9>>>為了防止字典的條目和關(guān)鍵字參數(shù)顯示傳遞的值發(fā)生沖突，關(guān)鍵字參數(shù)優(yōu)先，比如:
>>> from string import Template>>> msg = Template("It is $adj $msg")>>> adj = "interesting">>> print(msg.substitute(locals(), msg="message"))It is interesting message 以上這篇在Python中實現(xiàn)替換字符串中的子串的示例就是小編分享給大家的全部內(nèi)容了，希望能給大家一個參考，也希望大家多多支持VEVB武林網(wǎng)。
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