How do you find the index of a character in a string?

Question

I'm trying to create a program that finds the index of a character in a string,(without using any functions other than range,if statements, while loops,or for loops) but I can't figure out how to do it. Help would be greatly appreciated.

def findIndex(char, test):
    while char!=testList:
        for i in range(len(test)):
            if i!=char:
                i+=1
    if char==test:
        print i


print findIndex("e", "alphabet")

Answer 1

def find_index(needle, haystack):
    for i in range(len(haystack)):
        if needle == haystack[i]:
            return i
    else:
        return -1    # didn't find it

Answer 2

what is missing in your code:

1. NameError: testList variable is not define, so NameError exception will come.
2. range(): As range function return list of integers. In code you are checking integer value with character ie if i!=char: which must be like if test[i]==char and print or return in this if loop.
3. No need to while loop.
4. Last if loop: No need to last if loop. You are checking character with whole string which will never True. Only True when string with only one search character.

demo:

>>> range(3)
[0, 1, 2]

---

By enumerate :

1. Get character value from user by raw_input() . If user enters multiple characters then take first character for processing.
   2. Check character is present in target string. If not present then return -1 ie -1 means character is not found in string.
   3. Use enumerate() to iterate string.
   4. Check each items from the string is equal to search character or not.
   5. If yes then return index value.

code:

def findIndex(char, target_inoout):
    if char in target_inoout:
        for i, value in enumerate(target_inoout):
            if char==value:
                return i
    else:
        return -1



char = raw_input("Enter singal Character:").strip()[0]

rs = findIndex(char, "alphabet")
if rs==-1:
    print "Character %s is not found."%(char)
else:
    print "Character %s is found at: %d"%(char, rs)

output:

vivek@vivek:~/Desktop/stackoverflow$ python 31.py 
Enter singal Character:e
Character e is found at: 6
vivek@vivek:~/Desktop/stackoverflow$ python 31.py 
Enter singal Character:z
Character z is not found.
vivek@vivek:~/Desktop/stackoverflow$ 

---

For Multiple character in string:

code:

def findIndex(char, target_inoout):

    if char in target_inoout:
        result = []
        for i, value in enumerate(target_inoout):
            if char==value:
                result.append(i)
        return result
    else:
        return None



char = raw_input("Enter singal Character:").strip()[0]

rs = findIndex(char, "alphabet with some more values.")
if rs:
    print "Character %s is found at: %s"%(char, rs)
else:
    print "Character %s is not found."%(char)

Output:

vivek@vivek:~/Desktop/stackoverflow$ python 31.py 
Enter singal Character:m
Character m is found at: [16, 19]
vivek@vivek:~/Desktop/stackoverflow$ python 31.py 
Enter singal Character:z
Character z is not found.
vivek@vivek:~/Desktop/stackoverflow$