Python - String Method - format_map() Tutorial

This method is similar to format(**mapping), the only difference is format_map() will create a new dictionary during method call, while format(**mapping) just copy the dictionary.

Let see the difference between the both method.

example for format(**mapping)- 

point = {'x':'Python','y':'Fresherbell'}
print('Hello {x}, Hello {y}'.format(**point))
print('Hello {x}, Hello {y} {z}'.format(**point))

Output-

Hello Python, Hello Fresherbell
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
~\AppData\Local\Temp/ipykernel_6176/172717043.py in <module>
      1 point = {'x':'Python','y':'Fresherbell'}
      2 print('Hello {x}, Hello {y}'.format(**point))
----> 3 print('Hello {x}, Hello {y} {z}'.format(**point))

KeyError: 'z'

format(**mapping) is not good at handling missing key.

example for format_map()- 

class Default(dict):
    def __missing__(self, key):
        return key

point = {'x':['Python','World'],'y':'Fresherbell'}
print('Hello {x[1]}, Hello {y}'.format_map(point))
print('Hello {x[1]}, Hello {y} {z}'.format_map(Default(point)))

Output-

Hello World, Hello Fresherbell
Hello World, Hello Fresherbell z

format_map() is slightly fast and good in handling missing key with the help of class.