how to replace in a string

Question

i have a url, which have to alter base on output from other function.

rogues_detail_url = https://foo.bar.com/api/list_view.json?list=rogue_ap&fv_id=0&page_length=500&sort_col=acknowledged&sort_descend=false&start_row=0
rogues_detail_url.replace("500",foo())

foo() returns an integer value.

just in case if i was doing it wrong i also tried rogues_detail_url.replace("500","1000")

Neither of them seem to work. Printing the url after i execute the statement, prints the same url

`rogues_detail_url = rogues_detail_url.replace("500", str(foo()))`? — David Zemens, Jun 17 '19 at 23:53
Did you mean to put quotes around the string on the first statement? — Deepstop, Jun 17 '19 at 23:53
`replace` doesn't *modify* the string, it *returns* the modified string :) — David Zemens, Jun 17 '19 at 23:53

score 0 · Accepted Answer · answered Jun 18 '19 at 00:18

In python, strings are never modified in-place. In fact, strings can't be modified at all. As such, methods such as string.replace return a modified copy.

In python, string methods generally do the following:

copy the original
modify the copy in some way
leave the original alone.
return the modified copy

You want to write: new_string = old_string.replace("500","1000")

If you write only write old_string.replace("500","1000") then you just ignored/discarded the new modified string. old_string cannot be modified by replace or any other string method.

how to replace in a string

1 Answers1