How to do searching in Python?

Flora 180 Published: 09/08/2024

How to do searching in Python?

I'd be happy to help with that! Searching in Python involves using various techniques and libraries to find specific data within a dataset. Here are some common ways to search in Python:

Linear Search: This is the most basic form of search. You iterate over each element in the list and check if it matches what you're looking for. The time complexity for this method is O(n), where n is the number of elements in the list.

Example:

def linear_search(lst, target):

for i, item in enumerate(lst):


if item == target:


return i


return -1


my_list = [1, 2, 3, 4, 5]


index = linear_search(my_list, 3)


print(index)  # Output: 2
Binary Search: This method is more efficient than linear search when the list is sorted. You divide the list in half and keep searching until you find what you're looking for. The time complexity for this method is O(log n).

Example:

def binary_search(lst, target):

low, high = 0, len(lst) - 1


while low <= high:


mid = (low + high) // 2


if lst[mid] == target:


return mid


elif lst[mid] < target:


low = mid + 1


else:


high = mid - 1


return -1


my_list = [1, 2, 3, 4, 5]


index = binary_search(my_list, 3)


print(index)  # Output: 2
Search using dictionaries: If you're searching for a specific value within a dictionary, you can use the in operator.

Example:

my_dict = {'a': 1, 'b': 2, 'c': 3}

key = 'b'


if key in my_dict:


print(f"'{key}' is present in the dictionary.")


else:


print(f"'{key}' is not present in the dictionary.")
Search using sets: If you're searching for a specific value within a set, you can use the in operator.

Example:

my_set = {1, 2, 3, 4, 5}

target = 3


if target in my_set:


print(f"'{target}' is present in the set.")


else:


print(f"'{target}' is not present in the set.")
Search using lists with specific values: If you're searching for a specific value within a list of objects, you can iterate over the list and check if any object matches what you're looking for.

Example:

class Person:

def init(self, name):


self.name = name


people = [Person('John'), Person('Mary'), Person('Jane')]


target_person = 'Mary'


for person in people:


if person.name == target_person:


print(f"Found {target_person}!")


break


else:


print(f"{target_person} not found.")
Search using pandas: If you're working with large datasets and want to search for specific values within a dataframe, you can use the loc or query methods.

Example:

import pandas as pd

df = pd.DataFrame({'Name': ['John', 'Mary', 'Jane'],


'Age': [25, 30, 35]})


target_person = 'Mary'


result = df.loc[df['Name'] == target_person]


print(result)  # Output:   Name  Age

Mary  30

or


query_result = df.query('Name == "' + target_person + '"')


print(query_result)

These are just a few examples of how to search in Python. The best method for you will depend on the structure and size of your dataset, as well as what you're searching for.

How does find() work in Python?

I'll respond in English since that's what you requested!

In Python, the find() method is used to search for a specific substring or pattern within a string. It returns the index of the first occurrence of the specified value, or -1 if it's not found.

Here's a breakdown of how find() works:

Argument: The find() method takes one argument: the substring or pattern you want to search for. This can be a simple string, a regular expression (regex), or even a compiled regex object. Search behavior: By default, find() performs an exact match. It looks for the specified value in the original order of characters within the input string. Indexing: The method returns the index (an integer) of the first occurrence of the specified value. This index is zero-based, meaning the first character has an index of 0. -1 return value: If find() doesn't find the specified value in the input string, it returns -1. This indicates that the search failed or the substring wasn't found. Case sensitivity: By default, find() is case-sensitive. If you want to perform a case-insensitive search, you can use the lower() method on both the input string and the search value before calling find(). Regex searching: As mentioned earlier, you can pass a regex pattern or object to find(). This enables more complex searches using syntax like ., ^, $, [...], ( ), etc.

Here's an example of how to use find():

my_string = "Hello, World!"

search_value = "World"


index = my_string.find(search_value)


print(index)  # Output: 7

In this case, the method finds the first occurrence of "World" starting at index 7 (since indexing is zero-based).

When using regular expressions with find(), you can use the re module and pass a compiled regex object:

import re

my_string = "Hello, World!"


search_pattern = r"bworldb"


match_obj = re.compile(search_pattern)


index = my_string.find(match_obj.search(my_string).group())


print(index)  # Output: 7

In this example, we create a compiled regex pattern r"bworldb" that matches the whole word "World". We then use the search() method to find the first occurrence of this pattern in the input string and return its index.

That's a basic overview of how Python's find() method works!

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