Str is already defined as a global variable

Question

I noticed something really strange while working with functions. It looks like the variable name 'str' is already defined as a global variable. Take a look:

def Example(x):
   str = input()
   return str

print (Example(str))
#When typing 'Hello!' Output --> Hello! 

The variable str is defined in the function Example. So why is there no NameError: name 'str' is not defined?

When I call the variable x or something else ( In this case 'bar'):

def Example(x):
   bar = input()
   return bar

print (Example(bar))
#Output: NameError: name 'bar'is not defined

Why does a variable with the name 'str' act as a global variable?

Answer 1

In python, str() is the string constructor. It is used to cast an object to a string.

You can use it locally, but it will override the access to the function. You will not be able to use str() anymore.

for reference: https://docs.python.org/2/library/functions.html#str

class str(object='')

Return a string containing a nicely printable representation of an object. For strings, this returns the string itself. The difference with repr(object) is that str(object) does not always attempt to return a string that is acceptable to eval(); its goal is to return a printable string. If no argument is given, returns the empty string, ''.

For general knowledge purpose, you can get back you constructor if you delete your variable. For example:

test = 1
str(test)
>>>'1'

str = 2
str(test)
>>>TypeError: 'int' object is not callable

del str

str(test)
>>>'1'