Python String filter

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I am trying to solve a class assignment as listed below

Use lambda expressions and the filter() function to filter out words from a list that don't start with the letter 's'. For example:

seq = ['soup','dog','salad','cat','great']

should be filtered down to:

['soup','salad'] 

I wrote the following two sets of code...

seq = ['soup', 'dog','salad', 'cat', 'great']
result = filter (lambda test: test[0] == "s",seq)
print (result)

seq = ['soup', 'dog','salad', 'cat', 'great']
def checkf (input):
    if input[0]=='s':
            a = "TRUE"
    return(a)
test = seq[0]
result = filter (checkf(test),seq)
print (result)

Both codes give a strange answer filter object at 0x112aa06d8 as if it is returning a memory address in hexadecimal... What's wrong?


In python 3, filter objects are iterators. To print the contents, you have to materialize it into a sequence first, so try:

print( list(result))

See also: How to use filter, map, and reduce in Python 3

Python filter(), Here, we have a random list of number, string and boolean in randomList . We pass randomList to the filter() method with first parameter (filter function) as None . Python filter () function applies another function on a given iterable (List/String/Dictionary, etc.) to test which of its item to keep or discard. In simple words, it filters the ones that don’t pass the test and returns the rest as a filter object. The filter object is of the iterable type.


To use lambda and filter to resolve this problem, you need to specify that the result of your code will be a list.

So the following will work:

seq = ['soup', 'dog','salad', 'cat', 'great']
list(filter (lambda test: test[0] == "s",seq))

or (assigning to an object):

seq = ['soup', 'dog','salad', 'cat', 'great']
result = list(filter (lambda test: test[0] == "s",seq))
print(result)

The result of the two codes will be:

['soup', 'salad']

Python : filter() function, Python provides a method to filter out contents from a given sequence that can be a list, string or tuple etc. filter(function, iterable). Python uses list data type to store multiple data in a sequential index. It works like a numeric array of other programming languages. filter() method is a very useful method of Python. One or more data values can be filtered from any string or list or dictionary in Python by using filter() method. It filters data based on any particular condition.


This is the below code where your seq can be solved according to the lambda function.

seq = ['soup', 'dog','salad', 'cat', 'great']
result = list(filter (lambda test: test[0] == "s",seq))
print(result)

output: ['soup', 'salad']

using it in a function

seq = ['soup', 'dog','salad', 'cat', 'great']
def check(input):
    result = list(filter (lambda test: test[0] == "s",seq))
    return result

check(seq)

output: ['soup', 'salad']

Filtering Characters from a String, Filtering Characters from a String [duplicate] · python string iteration. This question already has answers here: Remove specific characters from  Filter a list of strings in Python using filter() Suppose we have a list of strings i.e. # List of string listOfStr = ['hi', 'this' , 'is', 'a', 'very', 'simple', 'string' , 'for', 'us'] Now let’s filter the contents of list and keep the strings with length 2 only using filter() i.e.


Python, Given two lists of strings string and substr, write a Python program to filter out all the strings in string that contains string in substr. Examples: Input : string = ['city1'​  def filter_string(str1, str2): for c in str2: str1 = str1.replace(c, '') return str1 Or a simple list comprehension: ''.join(c for c in str1 if c not in str2)


Lambda and filter in Python Examples, https://www.geeksforgeeks.org/reverse-string-python-5-different-ways/. result = list ( filter ( lambda x: (x = = "".join( reversed (x))), my_list)). # printing the result. The most popular usage of the filter () function is using Python List. We will provide a list which will be filtered with the given function. In this example, we will provide the list named numbers and use oddF'lter () function in order to filter numbers.


Python Filter() Function with List, String, Dictionary Examples, Python filter() function applies another function on a given iterable (List/String/​Dictionary, etc.) to test which of its item to keep or discard. In simple words, it filters  The zfill() method adds zeros (0) at the beginning of the string, until it reaches the specified length. If the value of the len parameter is less than the length of the string, no filling is done.