YouTipPython3 Func Filter
# Python3 filter() Function
## Description
The **filter()** function is used to filter a sequence, removing elements that do not meet the specified condition. It returns an iterator object. To convert it to a list, you can use `list()`.
It takes two parameters: the first is a function, and the second is a sequence. Each element of the sequence is passed as an argument to the function for evaluation, which returns either `True` or `False`. Finally, the elements for which the function returned `True` are placed into a new list.
### Syntax
The syntax for the `filter()` method is:
```python
filter(function, iterable)
### Parameters
* `function` -- The test function.
* `iterable` -- The iterable object.
### Return Value
Returns an iterator object.
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## Examples
The following examples demonstrate the use of the `filter` function:
### Filter out all odd numbers from a list:
```python
#!/usr/bin/python3
def is_odd(n):
return n % 2 == 1
tmplist = filter(is_odd, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
newlist = list(tmplist)
print(newlist)
Output:
[1, 3, 5, 7, 9]
### Filter out numbers between 1 and 100 whose square root is an integer:
```python
#!/usr/bin/python3
import math
def is_sqr(x):
return math.sqrt(x) % 1 == 0
tmplist = filter(is_sqr, range(1, 101))
newlist = list(tmplist)
print(newlist)
Output:
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]