将一英文语句中所有单词的首字母转换成大写

可以使用 Python 中的 `.title()` 方法来实现：

sentence = "this is a sentence."
new_sentence = sentence.title()
print(new_sentence)  # 输出 "This Is A Sentence."

或者使用 `.split()` 方法将句子拆分成单词，再对每个单词的首字母进行大写转换，最后再组合成一个新的句子：

sentence = "this is a sentence."
words = sentence.split()
new_sentence = ""
for word in words:
    new_sentence += word.capitalize() + " "
print(new_sentence.strip())  # 输出 "This Is A Sentence."