如何替换字符串中第一次出现的子字符串？

Question

我有一个字符串this is a simple example. this is another simple example.和一个子字符串字典，该子字符串第一次出现的子字符串应替换为

substitutions = {
    "a": "no",
    "simple": "difficult",
}

结果字符串应为this is no difficult example. this is another simple example.。我该如何实施？

Answer 1

将str.replace与count参数一起使用

例如：

substitutions = {
    "a": "no",
    "simple": "difficult",
}

s = "this is a simple example. this is another simple example."

for k, v in substitutions.items():
    s = s.replace(k, v, 1)
print(s)