re.sub（）如何变异不可变的Python字符串？

Question

这里，字符串flight_details字符串已更改，但其id未更改，下面是代码及其输出：

import re

flight_details = "Flight Savana Airlines a2134"
print(id(flight_details))

print(re.sub(r"Flight", r"Plane", flight_details))
print(id(flight_details))

print(re.sub(r"Plane", r"Akash", flight_details))
print(id(flight_details))

输出：

27264016
Plane Savana Airlines a2134
27264016
Flight Savana Airlines a2134
27264016

Answer 1

id(flight_details)在调用re.sub后返回相同的值，因为 re.sub不会更改传递给它的字符串的值（flight_details）。它返回一个新字符串

例如：

import re

flight_details = "Flight Savana Airlines a2134"
print(flight_details)
print(id(flight_details))

re.sub(r"Flight", r"Plane", flight_details)
print(flight_details)
print(id(flight_details))

flight_details = re.sub(r"Flight", r"Plane", flight_details)
print(flight_details)
print(id(flight_details))

输出：

Flight Savana Airlines a2134
1442959741216
Flight Savana Airlines a2134
1442959741216
Plane Savana Airlines a2134
1442959741456

见：https://docs.python.org/3/library/re.html#re.sub