1, the analytical expression (expression is str type) ---- The most common
a = 12
b = "Network"
result1 = eval(a+3) # result1 = 15
result2 = eval ( "News" + b) # result2 = "News Network"
2, the string transfer list
Requires quotation marks to wrap the content must be a list
Right: "[2, 'a']"
Error: "2, a" # turn after a tuple, and the content is not correct
Error: "[2, a]" # turn results after error
3, the string transfer dict
Requirements quotes wrap content must be Dictionary
正确：'{"name":"tom","age":18}
’
正确：'{"name":"tom","infos":{"size":345}}
’
4, the string switch tuple
Requirements quotes wrap content must be tuple
正确：'(2,"a","y")'