Why does bash display `>` instead of executing my command?

Your last quote is a round one, so the string you are passing to python is not finished. You can see the difference in the syntactic coloration:

smc -k F0Mx -w $(python -c 'print hex(2800 << 2)[2:]’)

vs

smc -k F0Mx -w $(python -c 'print hex(2800 << 2)[2:]')

The > you are seeing is because the shell is still waiting on input. As fredtantini's answer stated you have not correctly closed your statement.

There are other times you'd see the secondary input prompt (called PS2 in Bash). Certain interactive commands such as mailx will use this to fill in email fields. You can close a secondary input prompt by sending EOF to the shell by pressing Ctrl+D.

Problem

As Everyone else has said, the OP has an unterminated string in your python statement. You confused a rounded quote with a single quote.

Intended Usage

Seeing as the OP didn't know about the Secondary Prompt, I wanted to show the OP an example taken from the Linux From Scratch - Version 7.6 with SystemD book, and explain how this works. This is how the prompt is used in most cases:

cat > version-check.sh << "EOF"
#!/bin/bash
# Simple script to list version numbers of critical development tools

export LC_ALL=C
bash --version | head -n1 | cut -d" " -f2-4
echo "/bin/sh -> `readlink -f /bin/sh`"
echo -n "Binutils: "; ld --version | head -n1 | cut -d" " -f3-
bison --version | head -n1
if [ -e /usr/bin/yacc ];
  then echo "/usr/bin/yacc -> `readlink -f /usr/bin/yacc`";
  else echo "yacc not found"; fi

bzip2 --version 2>&1 < /dev/null | head -n1 | cut -d" " -f1,6-
echo -n "Coreutils: "; chown --version | head -n1 | cut -d")" -f2
diff --version | head -n1
find --version | head -n1
gawk --version | head -n1
if [ -e /usr/bin/awk ];
  then echo "/usr/bin/awk -> `readlink -f /usr/bin/awk`";
  else echo "awk not found"; fi

gcc --version | head -n1
g++ --version | head -n1
ldd --version | head -n1 | cut -d" " -f2-  # glibc version
grep --version | head -n1
gzip --version | head -n1
cat /proc/version
m4 --version | head -n1
make --version | head -n1
patch --version | head -n1
echo Perl `perl -V:version`
sed --version | head -n1
tar --version | head -n1
xz --version | head -n1

echo 'main(){}' > dummy.c && g++ -o dummy dummy.c
if [ -x dummy ]
  then echo "g++ compilation OK";
  else echo "g++ compilation failed"; fi
rm -f dummy.c dummy

EOF

Reasoning

The only tool Linux from Scratch makes extensive use of is the Terminal. In order to make sure that the book breaks away from the host build version, the book instructs you to type all scripts and config files using the behavior the OP thought was a problem. The first line creates a here document that will have the name version-check.sh when finished. Below is a screenshot from a Cygwin Terminal of the completed script:

Notice that the script contains CR/LF's which create whitespace in the document and increase readability. Every CR/LF creates a new instance of >, and by the end at the EOF, all the >'s create the buffer that becomes version-check.sh.