String
Contents
2.1. String¶
2.1.1. Control the Number of Printed Decimals with f-Strings¶
If you want to limit the number of decimals being printed, use the f-string as shown below.
num = 2.3123
print(f'{num:.1f}') # Limit to 1 decimal
print(f'{num:.2f}') # Limit to 2 decimals
2.3
2.31
2.1.2. Format Dates in Python f-Strings¶
When printing a Python string, f-strings allow you to format datetime easily with a curly bracket and its formats.
Find all formats here.
from datetime import datetime
date = datetime(2022, 1, 1, 15, 30, 45)
print(f'You need to be here at'
f' {date:%I:%M %p} on {date:%A}')
You need to be here at 03:30 PM on Saturday
2.1.3. String find: Find The Index of a Substring in a Python String¶
If you want to find the index of a substring in a string, use find() method. This method will return the index of the first occurrence of the substring if found and return -1 otherwise.
sentence = "Today is Saturday"
# Find the index of first occurrence of the substring
sentence.find("day")
2
sentence.find("nice")
# No substring is found
-1
You can also provide the starting and stopping position of the search:
# Start searching for the substring at index 3
sentence.find("day", 3)
15
2.1.4. re.sub: Replace One String with Another String Using Regular Expression¶
If you want to either replace one string with another string or to change the order of characters in a string, use re.sub.
re.sub allows you to use a regular expression to specify the pattern of the string you want to swap.
In the code below, I replace 3/7/2021 with Sunday and replace 3/7/2021 with 2021/3/7.
import re
text = "Today is 3/7/2021"
match_pattern = r"(\d+)/(\d+)/(\d+)"
re.sub(match_pattern, "Sunday", text)
'Today is Sunday'
re.sub(match_pattern, r"\3-\1-\2", text)
'Today is 2021-3-7'
2.1.5. Split a String by Multiple Characters¶
Using str.split only allows you to split a string by one character.
sent = "Today-is a nice_day"
sent.split('-')
['Today', 'is a nice_day']
If you want to split a string by multiple characters, use re.split(). re uses regrex to split the string.
import re
# split by space, -, or _
re.split(" |-|_", sent)
['Today', 'is', 'a', 'nice', 'day']
2.1.6. Multiline Strings¶
If your Python string gets very long, you can break it up using parentheses or a backslash.
text = (
"This is a very "
"long sentence "
"that is made up."
)
text
'This is a very long sentence that is made up.'
text = "This is a very "\
"long sentence "\
"that is made up."
text
'This is a very long sentence that is made up.'
2.1.7. difflib.SequenceMatcher: Detect The “Almost Similar” Articles¶
When analyzing articles, different articles can be almost similar but not 100% identical, maybe because of the grammar, or because of the change in two or three words (such as cross-posting). How can we detect the “almost similar” articles and drop one of them? That is when difflib.SequenceMatcher comes in handy.
from difflib import SequenceMatcher
text1 = 'I am Khuyen'
text2 = 'I am Khuen'
print(SequenceMatcher(a=text1, b=text2).ratio())
0.9523809523809523
2.1.8. difflib.get_close_matches: Get a List of the Best Matches for a Certain Word¶
If you want to get a list of the best matches for a certain word, use difflib.get_close_matches.
from difflib import get_close_matches
tools = ['pencil', 'pen', 'erasor', 'ink']
get_close_matches('pencel', tools)
['pencil', 'pen']
To get closer matches, increase the value of the argument cutoff (default 0.6).
get_close_matches('pencel', tools, cutoff=0.8)
['pencil']