Python String index() Method
The index() function returns the index number of the first occurrence of a substring (plain text) in the specified string (case sensitive). It's the same as the find() function except that if the substring is not found, it raises a ValueError if the substring is not found or if the index is outside the scope of the search.
How to formulate it like this:
string. index(substring, start, end)Parameters:
substring : (required) A substring that must be searched for in the given string.
start ( optional ) : ( Optional ) The starting position where the sub-string within the string needs to be checked. The default is 0.
End ( ) : ( Optional ) The index of the end within the string that the search ends with. default is the end of string,
Return value: The index() function returns an integer of the index number of the first occurrence of a substring (plain text) in the specified string.
Errors and exceptions:
If the substring is not found or if the index is outside the scope of the search.
We will use the index() function without the optional ( start ) and ( end ) parameters.undefined We'll just use the substring parameter to find the index number of the first occurrence of a substring in the given string.
In the following example, we will search for the index number of the first occurrence of the substring represented by the word (obaid),
Example:
# The string to be searched
string = "learn python With ahmed obaid"
# Searches the given string for the index number of the first occurrence of the substring and returns an integer
print(string. index("obaid")The output will be:
24In the following example, we will use the index() function with optional (start) and (end) parameters.
Example
# The string to be searched
string = "learn python With ahmed obaid"
# Searches the given string for the index number of the last occurrence of the substring and returns an integer
# Noting that we started the search from index #2
print(string. index("py", 2))
# Searches the given string for the index number of the last occurrence of the substring and returns an integer
# Noting that we started the search process from index number 0 to the end index number 10
print(string. index("learn", 0, 10))
# Searches the given string for the index number of the last occurrence of the substring and returns an integer
# Noting that we started the search process from index number 2 to the end index number 30
print(string. index("obaid", 10, 30))The output will be:
6
0
24We will throw a ValueError if the substring is not found or if the index is outside the scope of the search.
Example:
# The string to be searched
string = "learn python With ahmed obaid"
# If the substring is not found or the index is outside the scope of the search
# We will get an error exception
print(string. index("Hello")The output will be:
Traceback (most recent call last): File "/usr/lib/python3.8/py_compile.py", line 144, in compile code = loader. source_to_code(source_bytes, dfile or file, File "", line 846, in source_to_code File "", line 219, in _call_with_frames_removed File "./prog.py", line 5 print(string.index("Hello") ^
SyntaxError: unexpected EOF while parsing
During handling of the above exception, another exception undefined occurred:
Traceback (most recent call last): File "", line 1, in File "/usr/lib/python3.8/py_compile.py", line 150, in compile raise py_exc
py_compile.PyCompileError: File "./prog.py", line 5 print(string.index("Hello") ^
SyntaxError: unexpected EOF while parsing
External sources:
Built-in functions - official Python documentation
If you have any questions or concerns, leave them in the comments
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Python python data types Python String string methods python String search functions in Python python string index method
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Ahmed Obaid
Hello, I am Ahmed Obaid, an Egyptian Arabic programmer. I would like to put my experiences learning Python on this site So that it will be a reference for you and me as well.
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