Can't access friends ids even if rate limit is not met



I am currently developing a twitter API using python language and Twython library. I fetched the rate-limit-remaining which always gives a value = 10 (it should be 15 and then decreasing). Even then the very next API call gives the error no 429 rate limit exceeded which is unexpected. I am crawling friend ids of about 1k users. If anyone has any solution please help me. Quick response is appreciated.