There are two string methods for this, find() and index(). The difference between the two is what happens when the search string isn't found. find() returns -1 and index() raises a ValueError.
Using find()
>>> myString = 'Position of a character'
>>> myString.find('s')
2
>>> myString.find('x')
-1
Using index()
>>> myString = 'Position of a character'
>>> myString.index('s')
2
>>> myString.index('x')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: substring not found
From the Python manual
string.find(s, sub[, start[, end]])
Return the lowest index in s where the substring sub is found such that sub is wholly contained ins[start:end]. Return-1on failure. Defaults for start and end and interpretation of negative values is the same as for slices.
And:
Answer from Eli Bendersky on Stack Overflow
string.index(s, sub[, start[, end]])
Likefind()but raiseValueErrorwhen the substring is not found.
There are two string methods for this, find() and index(). The difference between the two is what happens when the search string isn't found. find() returns -1 and index() raises a ValueError.
Using find()
>>> myString = 'Position of a character'
>>> myString.find('s')
2
>>> myString.find('x')
-1
Using index()
>>> myString = 'Position of a character'
>>> myString.index('s')
2
>>> myString.index('x')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: substring not found
From the Python manual
string.find(s, sub[, start[, end]])
Return the lowest index in s where the substring sub is found such that sub is wholly contained ins[start:end]. Return-1on failure. Defaults for start and end and interpretation of negative values is the same as for slices.
And:
string.index(s, sub[, start[, end]])
Likefind()but raiseValueErrorwhen the substring is not found.
Just for a sake of completeness, if you need to find all positions of a character in a string, you can do the following:
s = 'shak#spea#e'
c = '#'
print([pos for pos, char in enumerate(s) if char == c])
which will print: [4, 9]
There's a builtin method find on string objects.
s = "Happy Birthday"
s2 = "py"
print(s.find(s2))
Python is a "batteries included language" there's code written to do most of what you want already (whatever you want).. unless this is homework :)
find returns -1 if the string cannot be found.
Ideally you would use str.find or str.index like demented hedgehog said. But you said you can't ...
Your problem is your code searches only for the first character of your search string which(the first one) is at index 2.
You are basically saying if char[0] is in s, increment index until ch == char[0] which returned 3 when I tested it but it was still wrong. Here's a way to do it.
def find_str(s, char):
index = 0
if char in s:
c = char[0]
for ch in s:
if ch == c:
if s[index:index+len(char)] == char:
return index
index += 1
return -1
print(find_str("Happy birthday", "py"))
print(find_str("Happy birthday", "rth"))
print(find_str("Happy birthday", "rh"))
It produced the following output:
3
8
-1