Question: New MacBookPro running Catalina. I have a virtualenv with no additional libraries installed yet. When I try to install nltk with pip3 install nltk, I get the following long error. The gist of it being "Architecture Not Supported". I tried installing with pip3 install -U but got a similar failure. Below is the all of the terminal text beginning with the first error message.  ERROR: Command errored out with exit status 1: command: /Users/Jayco/projects/passgen/venv/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/setup.py'"'"'; __file__='"'"'/private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' bdist_wheel -d /private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-wheel-vixqiu0k cwd: /private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/ Complete output (114 lines): running bdist_wheel running build running build_py creating build creating build/lib.macosx-10.14.6-x86_64-3.8 creating build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/__init__.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/regex.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/_regex_core.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/test_regex.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex running build_ext building 'regex._regex' extension creating build/temp.macosx-10.14.6-x86_64-3.8 creating build/temp.macosx-10.14.6-x86_64-3.8/regex_3 xcrun -sdk macosx clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -iwithsysroot/System/Library/Frameworks/System.framework/PrivateHeaders -iwithsysroot/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.8/Headers -arch arm64 -arch x86_64 -I/Users/Jayco/projects/passgen/venv/include -I/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8 -c regex_3/_regex.c -o build/temp.macosx-10.14.6-x86_64-3.8/regex_3/_regex.o In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:11: In file included from /Library/Developer/CommandLineTools/usr/lib/clang/12.0.0/include/limits.h:21: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/limits.h:63: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/cdefs.h:807:2: error: Unsupported architecture #error Unsupported architecture ^ In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:11: In file included from /Library/Developer/CommandLineTools/usr/lib/clang/12.0.0/include/limits.h:21: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/limits.h:64: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/machine/limits.h:8:2: error: architecture not supported #error architecture not supported ^ In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:71: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_types.h:27: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:33: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/machine/_types.h:34:2: error: architecture not supported #error architecture not supported ^ In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:71: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_types.h:27: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:55:9: error: unknown type name '__int64_t' typedef __int64_t __darwin_blkcnt_t; /* total blocks */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:56:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_blksize_t; /* preferred block size */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:57:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_dev_t; /* dev_t */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:60:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_gid_t; /* [???] process and group IDs */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:61:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_id_t; /* [XSI] pid_t, uid_t, or gid_t*/ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:62:9: error: unknown type name '__uint64_t' typedef __uint64_t __darwin_ino64_t; /* [???] Used for 64 bit inodes */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:68:9: error: unknown type name '__darwin_natural_t' typedef __darwin_natural_t __darwin_mach_port_name_t; /* Used by mach */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:70:9: error: unknown type name '__uint16_t'; did you mean '__uint128_t'? typedef __uint16_t __darwin_mode_t; /* [???] Some file attributes */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:71:9: error: unknown type name '__int64_t' typedef __int64_t __darwin_off_t; /* [???] Used for file sizes */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:72:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_pid_t; /* [???] process and group IDs */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:73:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_sigset_t; /* [???] signal set */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:74:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_suseconds_t; /* [???] microseconds */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:75:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_uid_t; /* [???] user IDs */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:76:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_useconds_t; /* [???] microseconds */ ^ note: '__uint128_t' declared here In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:71: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_types.h:43:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_wctype_t; ^ note: '__uint128_t' declared here In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:75: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types/_va_list.h:31: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/machine/types.h:37:2: error: architecture not supported #error architecture not supported ^ fatal error: too many errors emitted, stopping now [-ferror-limit=] 20 errors generated. error: command 'xcrun' failed with exit status 1 ---------------------------------------- ERROR: Failed building wheel for regex Running setup.py clean for regex Failed to build regex Installing collected packages: tqdm, regex, nltk Running setup.py install for regex ... error ERROR: Command errored out with exit status 1: command: /Users/Jayco/projects/passgen/venv/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/setup.py'"'"'; __file__='"'"'/private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-record-2kbtvdvx/install-record.txt --single-version-externally-managed --compile --install-headers /Users/Jayco/projects/passgen/venv/include/site/python3.8/regex cwd: /private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/ Complete output (114 lines): running install running build running build_py creating build creating build/lib.macosx-10.14.6-x86_64-3.8 creating build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/__init__.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/regex.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/_regex_core.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex copying regex_3/test_regex.py -> build/lib.macosx-10.14.6-x86_64-3.8/regex running build_ext building 'regex._regex' extension creating build/temp.macosx-10.14.6-x86_64-3.8 creating build/temp.macosx-10.14.6-x86_64-3.8/regex_3 xcrun -sdk macosx clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -iwithsysroot/System/Library/Frameworks/System.framework/PrivateHeaders -iwithsysroot/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.8/Headers -arch arm64 -arch x86_64 -I/Users/Jayco/projects/passgen/venv/include -I/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8 -c regex_3/_regex.c -o build/temp.macosx-10.14.6-x86_64-3.8/regex_3/_regex.o In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:11: In file included from /Library/Developer/CommandLineTools/usr/lib/clang/12.0.0/include/limits.h:21: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/limits.h:63: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/cdefs.h:807:2: error: Unsupported architecture #error Unsupported architecture ^ In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:11: In file included from /Library/Developer/CommandLineTools/usr/lib/clang/12.0.0/include/limits.h:21: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/limits.h:64: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/machine/limits.h:8:2: error: architecture not supported #error architecture not supported ^ In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:71: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_types.h:27: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:33: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/machine/_types.h:34:2: error: architecture not supported #error architecture not supported ^ In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:71: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_types.h:27: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:55:9: error: unknown type name '__int64_t' typedef __int64_t __darwin_blkcnt_t; /* total blocks */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:56:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_blksize_t; /* preferred block size */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:57:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_dev_t; /* dev_t */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:60:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_gid_t; /* [???] process and group IDs */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:61:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_id_t; /* [XSI] pid_t, uid_t, or gid_t*/ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:62:9: error: unknown type name '__uint64_t' typedef __uint64_t __darwin_ino64_t; /* [???] Used for 64 bit inodes */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:68:9: error: unknown type name '__darwin_natural_t' typedef __darwin_natural_t __darwin_mach_port_name_t; /* Used by mach */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:70:9: error: unknown type name '__uint16_t'; did you mean '__uint128_t'? typedef __uint16_t __darwin_mode_t; /* [???] Some file attributes */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:71:9: error: unknown type name '__int64_t' typedef __int64_t __darwin_off_t; /* [???] Used for file sizes */ ^ /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:72:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_pid_t; /* [???] process and group IDs */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:73:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_sigset_t; /* [???] signal set */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:74:9: error: unknown type name '__int32_t'; did you mean '__int128_t'? typedef __int32_t __darwin_suseconds_t; /* [???] microseconds */ ^ note: '__int128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:75:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_uid_t; /* [???] user IDs */ ^ note: '__uint128_t' declared here /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:76:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_useconds_t; /* [???] microseconds */ ^ note: '__uint128_t' declared here In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:71: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_types.h:43:9: error: unknown type name '__uint32_t'; did you mean '__uint128_t'? typedef __uint32_t __darwin_wctype_t; ^ note: '__uint128_t' declared here In file included from regex_3/_regex.c:48: In file included from /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/include/python3.8/Python.h:25: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:64: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_stdio.h:75: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types/_va_list.h:31: /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/machine/types.h:37:2: error: architecture not supported #error architecture not supported ^ fatal error: too many errors emitted, stopping now [-ferror-limit=] 20 errors generated. error: command 'xcrun' failed with exit status 1 ---------------------------------------- ERROR: Command errored out with exit status 1: /Users/Jayco/projects/passgen/venv/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/setup.py'"'"'; __file__='"'"'/private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-install-3izld5bk/regex/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /private/var/folders/t3/ccw8mfyj24s1cdsyrwtpb32r0000gp/T/pip-record-2kbtvdvx/install-record.txt --single-version-externally-managed --compile --install-headers /Users/Jayco/projects/passgen/venv/include/site/python3.8/regex Check the logs for full command output. 

Answer: I had the same problem with the default installed python. (pip3 install regex) When using python from brew it worked for me. Try this: brew install python3 /usr/local/bin/pip3 install nltk  or with a virtualenv: brew install python3 /usr/local/bin/python3 -m venv venv . venv/bin/activate pip install ntlk