find substring in string python using for loop

How to use for loop to find all instances of a substring in a string

stackoverflow.com › questions › 55365658 › how-to-use-for-loop-to-find-all-instances-of-a-substring-in-a-string

You are using the for loop wrong.

This takes each character in the string, assigns it to x, and prints it:

for x in 'aabfh':
    print (x)

This takes each character in the string, assigns it to list1[i], and prints it:

for list1[i] in 'aabfh':
    print(list1[i])

In your code, if you look at list1, you will find that it has been changed to ['h', 'h', 'h'] because that's what you told it to do (or at least as many h's as "some condition" will allow).

Answer from Kenny Ostrom on Stack Overflow

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stackoverflow.com › questions › 55365658 › how-to-use-for-loop-to-find-all-instances-of-a-substring-in-a-string

python - How to use for loop to find all instances of a substring in a string - Stack Overflow

Top answer

1 of 3

You are using the for loop wrong.

This takes each character in the string, assigns it to x, and prints it:

for x in 'aabfh':
    print (x)

This takes each character in the string, assigns it to list1[i], and prints it:

for list1[i] in 'aabfh':
    print(list1[i])

In your code, if you look at list1, you will find that it has been changed to ['h', 'h', 'h'] because that's what you told it to do (or at least as many h's as "some condition" will allow).

2 of 3

Your for loop raise NameError. you can't access to elements of a list in for loop like that. change it to this one to print your desired output:

for char in str1:
    if char in list1:
        print(char)

a
a
b

for printing its position you can use index:

for char in str1:
    if char in list1:
        print(list1.index(char))

0
0
1

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stackoverflow.com › questions › 18937562 › finding-substring-in-python

string - Finding substring in python - Stack Overflow

Top answer

1 of 3

Given:

s = 'ABCDEFGHIJKLMNOP'
targets = 'CDE','XYZ','JKL'

With loops:

for t in targets:
    for i in range(len(s) - len(t) + 1):
        for j in range(len(t)):
            if s[i + j] != t[j]:
                break
        else:
            print(s[i:])
            break
    else:
        print(t,'does not exist')

Pythonic way:

for t in targets:
    i = s.find(t)
    if i != -1:
        print(s[i:])
    else:
        print(t,'does not exist')

Output (in both cases):

CDEFGHIJKLMNOP
XYZ does not exist
JKLMNOP

2 of 3

Here's a concise way to do so:

s = "ABCDEFGHIJKLMNOP"
if "CDE" in s: 
    print s[s.find("CDE")+len("CDE"):]
else: 
    print s

Prints:

FGHIJKLMNOP

The caveat here is of course, if the sub-string is not found, the original string will be returned.

Why do this? Doing so allows you to check whether or not the original string was found or not. As such, this can be conceptualized into a simple function (warning: no type checks enforced for brevity - it is left up to the reader to implement them as necessary):

def remainder(string, substring):
    if substring in string:
        return string[string.find(substring)+len(substring):]
    else:
        return string

Discussions

Finding values in a string using for loops in Python 3 - Stack Overflow

I am writing a code that prompts the user to enter a sentence which is then defined as str1 and then is prompted to enter a word defined as str2. For example: Please enter a sentence: i like to More on stackoverflow.com

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What is the most efficient way to find substrings in strings?

Easiest solution is to just use the 'in' operator like this: if "Leonardo DiCaprio" in article_title: return True And according to the top answer here it's also the fastest: whats-a-faster-operation-re-match-search-or-str-find Edit:cant get that return statement to indent for the life of me, you get the idea More on reddit.com

r/learnpython

January 11, 2022

Using while loops to find a character in a string

s = "abcdef" currIndex = 0 length = len(s) while currIndex < length: if s[currIndex] == 'e': print(currIndex) currIndex += 1 create an index variable (currIndex) set to the starting point of the string, 0. create a limit variable for your index (length), in this case the limit is the length of the string. set your while loop to execute as long as currIndex is less than the limit. keep in mind the length of the string will always be one higher than the last index..hense "<" instead of "<=". the first character is at index 0, and the last is at len(s)-1. each iteration of the while loop checks if the character of s at currIndex is equal to the char you're looking for and prints currIndex if it is. increment currIndex by 1 More on reddit.com

r/learnprogramming

December 20, 2022

How do I check if string contains all substrings in list?

You could try

if all([val in string for val in list]):

Which checks the truth of each check and returns True only if all are True. Otherwise you're looking at a loop (or if your lists get really big a generator).

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