Anyone experienced anything like this? The behavior seems consistent but unexpected. python 3.6 on both windows (10) and linux (ubuntu 18.04) seem to exhibit the same odd behavior. something about a docker-image looking string seems to trigger this behavior. The behavior seems as expected for other strings. Python 3.6.5 |Anaconda, Inc.| (default, Mar 29 2018, 13:32:41) [MSC v.1900 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. sample_string_1 = "namespace/something-plugin-extra:dev" print(sample_string_1.lstrip("namespace/something-plugin")) xtra:dev print(sample_string_1.lstrip("namespace/something-plug")) xtra:dev print(sample_string_1.lstrip("namespace/something-plu")) xtra:dev print(sample_string_1.lstrip("namespace/something-pl")) ugin-extra:dev sample_string_1 = "namespace/something-plugxx-extra:dev" print(sample_string_1.lstrip("namespace/something-plugin")) xx-extra:dev print(sample_string_1.lstrip("namespace/something-plug")) xx-extra:dev print(sample_string_1.lstrip("namespace/something-plu")) xx-extra:dev print(sample_string_1.lstrip("namespace/something-pl")) ugxx-extra:dev Python 3.6.5 (default, Apr 1 2018, 05:46:30) [GCC 7.3.0] on linux Type "help", "copyright", "credits" or "license" for more information. sample_string_1 = "namespace/something-plugin-extra:dev" print(sample_string_1.lstrip("namespace/something-plugin")) xtra:dev print(sample_string_1.lstrip("namespace/something-plug")) xtra:dev print(sample_string_1.lstrip("namespace/something-plu")) xtra:dev print(sample_string_1.lstrip("namespace/something-pl")) ugin-extra:dev sample_string_1 = "namespace/something-plugxx-extra:dev" print(sample_string_1.lstrip("namespace/something-plugin")) xx-extra:dev print(sample_string_1.lstrip("namespace/something-plug")) xx-extra:dev print(sample_string_1.lstrip("namespace/something-plu")) xx-extra:dev print(sample_string_1.lstrip("namespace/something-pl")) ugxx-extra:dev