**`re.subn()`** belongs to the regular expressions (RE) module in Python and specifies strings or a set of strings or patterns that match it. To use this function, we need to import the RE module.

The `re.subn()` function is the same as the `re.sub()` function, except that it also provides a count of the number of replacements that it has done.

#    
## Syntax
```py
re.subn(pattern, repl, string, count=0, flags=0)
```

* The first parameter, `pattern`, denotes the string/pattern that needs to be replaced.

* The second parameter, `repl`, denotes the string/pattern with which the pattern is replaced.

* The third parameter, `string`, denotes the string on which the `re.subn()` operation will take place.

* The fourth parameter, `count`, denotes the number of replacements that should occur on which the `re.subn()` operation will take place.

* The fifth parameter, `flags`, helps to shorten the code and has similar functions as that of split operations.

## Code

Let us look at the code snippet below:


# Importing re module
import re

# Given String
s = "I am a human being."

# Performing the subn() operation
res_1 = re.subn('a', 'x', s)
res_2 = re.subn('[a,I]','x',s)

# Print Results
print(res_1)
print(res_2)



#    
## Explanation

* *In line 2,* we import the `re` module.

* *In line 5,* we take a sample string.

* *In line 8,* we use the `re.subn()` function to replace all the *a's* with *x's* in the string *s*.  Since the number of replacements is three, it has been provided in the tuple as an output.

* *In line 9,* we use the `re.subn()` function to replace all the *a's* and *I's* with *x's* in the string *s*. Since the number of replacements is four, it has been provided in the tuple as an output.

* *In lines 12 and 13,* we print the results.


What is the re.subn() function in Python?

Python's re.subn() in the RE module replaces patterns in strings and returns a count of replacements.