I have the following list
l=['web','python']
and the following string
st='python, C, something, find'
I want to check if any element in the list is in the string
I tried using
any(x in l for x in st)
however it gives false
seems python can't recognize the element in the string, is there a way to check elements from list to a string if there is a match. i did it successfully using a for a loop and splitting the string to a list however that is not efficient with the real data as it contain a long lists and strings. need something efficient.
thanks
You would first need to split the string, or else you will be iterating over the individual characters.
Try this:
l=['web','python']
st='python, C, something, find'
any([x in l for x in st.split(',')]) # True
But this isn't the most efficient. For better performance, you could take a look into using a trie.
If your would like to check if any element in the list is in the string
then your code should be
any(x in st for x in l)
You can use this method
word_list = ['web','python']
string = 'python, C, something, find'
exist = filter(lambda x : x in string , word_list)
print(list(exist))
output:
['python']
You were close. How about:
any(x in l for x in st.replace(',', '').split())
which returns:
True
A different approach:
import re
re.search(r'\b(' + '|'.join(l) + r')\b', st)
The search will return None if there's no match and the match if there is one. You can use it like:
if re.search(r'\b(' + '|'.join(l) + r')\b', st):
print(f'there was a match: {t.groups()}')
else:
print('no match')
Related
I working on a simple algorithm which prints the first character who occurred twice or more.
for eg:
string ='abcabc'
output = a
string = 'abccba'
output = c
string = 'abba'
output = b
what I have done is:
string = 'abcabc'
s = []
for x in string:
if x in s:
print(x)
break
else:
s.append(x)
output: a
But its time complexity is O(n^2), how can I do this in O(n)?
Change s = [] to s = set() (and obviously the corresponding append to add). in over set is O(1), unlike in over list which is sequential.
Alternately, with regular expressions (O(n^2), but rather fast and easy):
import re
match = re.search(r'(.).*\1', string)
if match:
print(match.group(1))
The regular expression (.).*\1 means "any character which we'll remember for later, any number of intervening characters, then the remembered character again". Since regexp is scanned left-to-right, it will find a in "abba" rather than b, as required.
Use dictionaries
string = 'abcabc'
s = {}
for x in string:
if x in s:
print(x)
break
else:
s[x] = 0
or use sets
string = 'abcabc'
s = set()
for x in string:
if x in s:
print(x)
break
else:
s.add(x)
both dictionaries and sets use indexing and search in O(1)
I'm trying to make a function, f(x), that would add a "-" between each letter:
For example:
f("James")
should output as:
J-a-m-e-s-
I would love it if you could use simple python functions as I am new to programming. Thanks in advance. Also, please use the "for" function because it is what I'm trying to learn.
Edit:
yes, I do want the "-" after the "s".
Can I try like this:
>>> def f(n):
... return '-'.join(n)
...
>>> f('james')
'j-a-m-e-s'
>>>
Not really sure if you require the last 'hyphen'.
Edit:
Even if you want suffixed '-', then can do like
def f(n):
return '-'.join(n) + '-'
As being learner, it is important to understand for your that "better to concat more than two strings in python" would be using str.join(iterable), whereas + operator is fine to append one string with another.
Please read following posts to explore further:
Any reason not to use + to concatenate two strings?
which is better to concat string in python?
How slow is Python's string concatenation vs. str.join?
Also, please use the "for" function because it is what I'm trying to learn
>>> def f(s):
m = s[0]
for i in s[1:]:
m += '-' + i
return m
>>> f("James")
'J-a-m-e-s'
m = s[0] character at the index 0 is assigned to the variable m
for i in s[1:]: iterate from the second character and
m += '-' + i append - + char to the variable m
Finally return the value of variable m
If you want - at the last then you could do like this.
>>> def f(s):
m = ""
for i in s:
m += i + '-'
return m
>>> f("James")
'J-a-m-e-s-'
text_list = [c+"-" for c in text]
text_strung = "".join(text_list)
As a function, takes a string as input.
def dashify(input):
output = ""
for ch in input:
output = output + ch + "-"
return output
Given you asked for a solution that uses for and a final -, simply iterate over the message and add the character and '-' to an intermediate list, then join it up. This avoids the use of string concatenations:
>>> def f(message)
l = []
for c in message:
l.append(c)
l.append('-')
return "".join(l)
>>> print(f('James'))
J-a-m-e-s-
I'm sorry, but I just have to take Alexander Ravikovich's answer a step further:
f = lambda text: "".join([c+"-" for c in text])
print(f('James')) # J-a-m-e-s-
It is never too early to learn about list comprehension.
"".join(a_list) is self-explanatory: glueing elements of a list together with a string (empty string in this example).
lambda... well that's just a way to define a function in a line. Think
square = lambda x: x**2
square(2) # returns 4
square(3) # returns 9
Python is fun, it's not {enter-a-boring-programming-language-here}.
I have this code:
import nltk
import pypyodbc
text = raw_input()
token = nltk.word_tokenize(text) //return a list value
def search(self, lists):
if not self.connected:
self.connect()
for word in lists:
self.cur.execute('SELECT Ybanag FROM Words WHERE English IN (%s)' % (','.join('?'*len(lists))), lists)
result = self.cur.fetchall()
return result
wherein the output is a list of single element tuple (ex. I enter we all there):
[('tore',), ('ngaming',), ('sittam',)] (translate the input into mother tongue language). I want that the output will be converted into string to eliminate the [],(),'',' symbols. How to convert it into string?
You have to use str.join method.
>>> a = [('tore',), ('ngaming',), ('sittam',)]
>>> " ".join([x[0] for x in a])
'tore ngaming sittam'
I would just use a for loop. You can loop through the list of tuples and add each element to an empty string variable
x = [('tore'), ('ngaming'), ('sittam')]
z = ""
for i in x:
z = z + i + " "
print z
After seeing Lafada's answer, I realized that list comprehension and str.join is the best option. Though his answer is better, this is basically what his answer does, just done more manually.
Like, for example, I have the string '12345' and the string '+*' and I want to make it so that the new string would be '1+2*3+4*5', alternating between the two characters in the second string. I know how to do it with one character using join(), but I just can't figure out how to do it with both alternating. Any help would be greatly appreciated. Thanks!
You could use itertools.cycle() to forever alternate between the characters:
from itertools import cycle
result = ''.join([c for pair in zip(inputstring, cycle('+*')) for c in pair])[:-1]
You do need to remove that last + added on, but this does work just fine otherwise:
>>> from itertools import cycle
>>> inputstring = '12345'
>>> ''.join([c for pair in zip(inputstring, cycle('+*')) for c in pair])[:-1]
'1+2*3+4*5'
import itertools
s = '12345'
op = '+*'
answer = ''.join(itertools.chain.from_iterable(zip(s, itertools.cycle(op))))[:-1]
print(answer)
Output:
1+2*3+4*5
You could use this code:
string = "12345"
separator = "+*"
result = ""
for i, c in enumerate(string): //enumerate returns a list of tuples [index, character]
t = i, c
result += t[1] //append character
if(t[0]==len(string)-1): //if reached max length
break
if(t[0]%2==0): //if even
result += separator[0] //append +
else:
result += separator[1] //append *
print(result) //otuput "1+2*3+4*5"
Following works without having to trim the end.
''.join(map(lambda x: x[0] + x[1],izip_longest('12345',''.join(repeat('*+',len('12345')/2)),fillvalue='')))
From python documentation;
itertools.izip_longest(*iterables[, fillvalue]): Make an iterator that aggregates elements from each of the iterables. If the iterables are of uneven length, missing values are filled-in with fillvalue. Iteration continues until the longest iterable is exhausted.
I am having trouble figuring out the following:
Suppose I have a list of strings
strings = ["and","the","woah"]
I want the output to be a list of strings where the ith position of every string becomes a new string item in the array like so
["atw","nho","dea","h"]
I am playing with the following list comprehension
u = [[]]*4
c = [u[i].append(stuff[i]) for i in range(0,4) for stuff in strings]
but its not working out. Can anyone help? I know you can use other tools to accomplish this, but i am particularly interested in making this happen with for loops and list comprehensions. This may be asking a lot, Let me know if I am.
Using just list comprehensions and for loops you can:
strings = ["and","the","woah"]
#Get a null set to be filled in
new = ["" for x in range(max([len(m) for m in strings]))]
#Cycle through new list
for index,item in enumerate(new):
for w in strings:
try:
item += w[index]
new[index] = item
except IndexError,err:
pass
print new
My idea would be to use itertools.izip_longest and a list comprehension.
>>> from itertools import izip_longest
>>> strings = ["and","the","woah"]
>>> [''.join(x) for x in izip_longest(*strings, fillvalue='')]
['atw', 'nho', 'dea', 'h']
Try
array = ["and","the","woah"]
array1 = []
longest_item = 0
for i in range(0,3): #length of array
if len(array[i]) > longest_item:
longest_item = len(array[i]) #find longest string
for i in range(0,longest_item):
str = ""
for i1 in range(0,3): #length of array
if len(array[i1]) < longest_item:
continue
str += array[i1][i:i+1]
array1.append(str)
I didn't actually try this code out, I just improvised it. Please leave a comment ASAP if you find a bug.