Yourdictionary.com and couple of others provide this definition for "assignment":

A position or post of duty to which one is assigned. The journalist took an assignment in China.

Is this the same as "a job". Does the sentence mean that the journalist took a job in China"

some other definitions state that it's 3. A piece of work that has been assigned:(source thefreedtionary)

Is assignment not only a piece of work but also your occupation? Something you do for a living. Can I say for example "My assignment for the last 20 years was a taxi driver"?

Yourdictionary.com and couple of others provide this definition for "assignment":

A position or post of duty to which one is assigned. The journalist took an assignment in China.

Is this the same as "a job"? Does the sentence mean that the journalist took a job in China?

Some other definitions state that it's:

A piece of work that has been assigned (source thefreedictionary)

Is assignment not only a piece of work but also your occupation? Something you do for a living. Can I say "My assignment for the last 20 years was a taxi driver"?