What does Python's eval() do?

Question

In the book that I am reading on Python, it keeps using the code eval(input(\'blah\'))

I read the documentation, and I understand it, but I still do no

Answer 1

One of useful applications of eval() is to evaluate python expressions from string. For example load from file string representation of dictionary:

running_params = {"Greeting":"Hello "}
fout = open("params.dat",'w')
fout.write(repr(running_params))
fout.close()

Read it out as a variable and edit it:

fin = open("params.dat",'r')
diction=eval(fin.read())
diction["Greeting"]+="world"
fin.close()
print diction

Output:

{'Greeting': 'Hello world'}