def fib(n): a,b=1,1 for i in range(n-1): a，b=b，a+b return a print(fib(7)

As an AI language model, I can see that there is a syntax error in the code. The line "a，b=b，a" should have a comma instead of a Chinese full-width comma.

Here is the corrected code:

def fib(n):
a,b=1,1
for i in range(n-1):
a,b=b,a+b
return a

print(fib(7))

This code defines a function fib(n) that calculates the nth Fibonacci number. The function starts with the first two Fibonacci numbers (1 and 1), and then iteratively calculates the next number in the sequence by adding the previous two numbers. The function returns the nth Fibonacci number.

In this example, the function is called with n=7, so it calculates the 7th Fibonacci number, which is 13. The result is printed using the print() function.