错误原因是缩进错误，您忘记了在最后一行之前的缩进块。在Python中，缩进不是可选的！
此外，要匹配develop之后的任意位数（包括0），您应该在\d之后添加*，以表示出现零次或更多次。
最后，您应该使用re.fullmatch而不是re.match来匹配整个字符串，而不仅仅是开头。

import re

# Target String one
str = ["develop","develop1","develop123","developtest","develop9_test"]

# pattern to find three consecutive digits
# compile string pattern to re.Pattern object
for i in range(0, len(str)):
  if re.fullmatch(r"develop\d*", str[i]):
    print("true")

要检查特定Patten中的字符串，请执行以下操作：

import re

# Target String one
str_list = ["develop","develop1","develop123","developtest","develop9_test"]

# pattern to find three consecutive digits
pattern = r"develop\d{3}"

# compile string pattern to re.Pattern object
regex = re.compile(pattern)

for s in str_list:
    if regex.search(s):
        print(f"'{s}' matches the pattern '{pattern}'")
    else:
        print(f"'{s}' does not match the pattern '{pattern}'")