例如：
print(", ".join(["spam", "eggs", "ham"]))
# 输出结果 "spam, eggs, ham"
print("Hello ME".replace("ME", "world"))
# 输出结果 "Hello world"
print("This is a sentence.".startswith("This"))
# 输出结果 "True"
print("This is a sentence.".endswith("sentence."))
# 输出结果 "True"
print("This is a sentence.".upper())
# 输出结果 "THIS IS A SENTENCE."
print("AN ALL CAPS SENTENCE".lower())
# 输出结果 "an all caps sentence"
print("spam, eggs, ham".split(", "))
# 输出结果"['spam', 'eggs', 'ham']"