I have a string 'A1T1730'
From this I need to extract the second letter and the last four letters. For example, from 'A1T1730' I need to extract '1' and '1730'. I'm not sure how to do this in Python.
I have the following right now which extracts every character from the string separately so can someone please help me update it as per the above need.
list = ['A1T1730']
for letter in list[0]:
print letter
Which gives me the result of A, 1, T, 1, 7, 3, 0
my_string = "A1T1730"
my_string = my_string[1] + my_string[-4:]
print my_string
Output
11730
If you want to extract them to different variables, you can just do
first, last = my_string[1], my_string[-4:]
print first, last
Output
1 1730
Using filter with str.isdigit (as unbound method form):
>>> filter(str.isdigit, 'A1T1730')
'11730'
>>> ''.join(filter(str.isdigit, 'A1T1730')) # In Python 3.x
'11730'
If you want to get numbers separated, use regular expression (See re.findall):
>>> import re
>>> re.findall(r'\d+', 'A1T1730')
['1', '1730']
Use thefourtheye's solution if the positions of digits are fixed.
BTW, don't use list as a variable name. It shadows builtin list function.
Well you could do like this
_2nd = lsit[0][1]
# last 4 characters
numbers = list[0][-4:]
You can use the function isdigit(). If that character is a digit it returns true and otherwise returns false:
list = ['A1T1730']
for letter in list[0]:
if letter.isdigit() == True:
print letter, #The coma is used for print in the same line
I hope this useful.
Related
If I have this string "for[4t]" and I want to pick "4". But the number can change: the string can be "for[12t]", "for[342424t]", ect.. how I pick this number?
I can't use str.replace('for[', '').replace('t]'), because the rest of the string after this can change.
You can get the variable with a regular expression. In this example, "for[" and "t]" are constant, and you want a variable number of digits inside. In a regular expression, [ is a special character so needs to be escaped. () selects a group of characters you want to capture, and \d+ says "any number of digits (but at least one)".
>>> import re
>>> test = "for[4t]"
>>> re.match(r"for\[(\d+)t]", test).group(1)
'4'
>>> test = "for[342424t]"
>>> re.match(r"for\[(\d+)t]", test).group(1)
'342424'
>>> test = "for[342424t] and other stuff"
>>> re.match(r"for\[(\d+)t]", test).group(1)
'342424'
Here is a way to do it
import re
strings = ["for[4t]", "for[12t]", "for[342424t]"]
for string in strings:
print(re.findall(r"for\[([0-9]+)t", string)[0])
# define some sample message
message = "hello for[555t] goodbye"
# find the first [
bracket_location = message.find("[")
# declare a variable for picking the number
pick_number = ''
# loop over the contents of message, starting one character past
# the bracket
for ch in message[bracket_location+1:]:
# if this is not a digit, break the loop
if not ch.isdigit():
break
# add this digit to the pick number
pick_number += ch
# we're done, print the number we picked
print(pick_number)
lets say the variable string holds the string, and the variable number will hold the number that you want.
if you wat number to have type string:
number = string[string.index("[")+1:string.index("t]")]
if you want number to have type integer:
number = int(string[string.index("[")+1:string.index("t]")])
This only works if the number is between [ and t], and if those are the first two instances of [ and t] in the string
There is a string, for example. EXAMPLE.
How can I remove the middle character, i.e., M from it? I don't need the code. I want to know:
Do strings in Python end in any special character?
Which is a better way - shifting everything right to left starting from the middle character OR creation of a new string and not copying the middle character?
In Python, strings are immutable, so you have to create a new string. You have a few options of how to create the new string. If you want to remove the 'M' wherever it appears:
newstr = oldstr.replace("M", "")
If you want to remove the central character:
midlen = len(oldstr) // 2
newstr = oldstr[:midlen] + oldstr[midlen+1:]
You asked if strings end with a special character. No, you are thinking like a C programmer. In Python, strings are stored with their length, so any byte value, including \0, can appear in a string.
To replace a specific position:
s = s[:pos] + s[(pos+1):]
To replace a specific character:
s = s.replace('M','')
This is probably the best way:
original = "EXAMPLE"
removed = original.replace("M", "")
Don't worry about shifting characters and such. Most Python code takes place on a much higher level of abstraction.
Strings are immutable. But you can convert them to a list, which is mutable, and then convert the list back to a string after you've changed it.
s = "this is a string"
l = list(s) # convert to list
l[1] = "" # "delete" letter h (the item actually still exists but is empty)
l[1:2] = [] # really delete letter h (the item is actually removed from the list)
del(l[1]) # another way to delete it
p = l.index("a") # find position of the letter "a"
del(l[p]) # delete it
s = "".join(l) # convert back to string
You can also create a new string, as others have shown, by taking everything except the character you want from the existing string.
How can I remove the middle character, i.e., M from it?
You can't, because strings in Python are immutable.
Do strings in Python end in any special character?
No. They are similar to lists of characters; the length of the list defines the length of the string, and no character acts as a terminator.
Which is a better way - shifting everything right to left starting from the middle character OR creation of a new string and not copying the middle character?
You cannot modify the existing string, so you must create a new one containing everything except the middle character.
Use the translate() method:
>>> s = 'EXAMPLE'
>>> s.translate(None, 'M')
'EXAPLE'
def kill_char(string, n): # n = position of which character you want to remove
begin = string[:n] # from beginning to n (n not included)
end = string[n+1:] # n+1 through end of string
return begin + end
print kill_char("EXAMPLE", 3) # "M" removed
I have seen this somewhere here.
card = random.choice(cards)
cardsLeft = cards.replace(card, '', 1)
How to remove one character from a string:
Here is an example where there is a stack of cards represented as characters in a string.
One of them is drawn (import random module for the random.choice() function, that picks a random character in the string).
A new string, cardsLeft, is created to hold the remaining cards given by the string function replace() where the last parameter indicates that only one "card" is to be replaced by the empty string...
On Python 2, you can use UserString.MutableString to do it in a mutable way:
>>> import UserString
>>> s = UserString.MutableString("EXAMPLE")
>>> type(s)
<class 'UserString.MutableString'>
>>> del s[3] # Delete 'M'
>>> s = str(s) # Turn it into an immutable value
>>> s
'EXAPLE'
MutableString was removed in Python 3.
Another way is with a function,
Below is a way to remove all vowels from a string, just by calling the function
def disemvowel(s):
return s.translate(None, "aeiouAEIOU")
Here's what I did to slice out the "M":
s = 'EXAMPLE'
s1 = s[:s.index('M')] + s[s.index('M')+1:]
To delete a char or a sub-string once (only the first occurrence):
main_string = main_string.replace(sub_str, replace_with, 1)
NOTE: Here 1 can be replaced with any int for the number of occurrence you want to replace.
You can simply use list comprehension.
Assume that you have the string: my name is and you want to remove character m. use the following code:
"".join([x for x in "my name is" if x is not 'm'])
If you want to delete/ignore characters in a string, and, for instance, you have this string,
"[11:L:0]"
from a web API response or something like that, like a CSV file, let's say you are using requests
import requests
udid = 123456
url = 'http://webservices.yourserver.com/action/id-' + udid
s = requests.Session()
s.verify = False
resp = s.get(url, stream=True)
content = resp.content
loop and get rid of unwanted chars:
for line in resp.iter_lines():
line = line.replace("[", "")
line = line.replace("]", "")
line = line.replace('"', "")
Optional split, and you will be able to read values individually:
listofvalues = line.split(':')
Now accessing each value is easier:
print listofvalues[0]
print listofvalues[1]
print listofvalues[2]
This will print
11
L
0
Two new string removal methods are introduced in Python 3.9+
#str.removeprefix("prefix_to_be_removed")
#str.removesuffix("suffix_to_be_removed")
s='EXAMPLE'
In this case position of 'M' is 3
s = s[:3] + s[3:].removeprefix('M')
OR
s = s[:4].removesuffix('M') + s[4:]
#output'EXAPLE'
from random import randint
def shuffle_word(word):
newWord=""
for i in range(0,len(word)):
pos=randint(0,len(word)-1)
newWord += word[pos]
word = word[:pos]+word[pos+1:]
return newWord
word = "Sarajevo"
print(shuffle_word(word))
Strings are immutable in Python so both your options mean the same thing basically.
If I am building a basic encryption program in python that reassigns A to C and D to F and so on, what is a simple algorithm I could use to do this?
I have a list named alphabet that holds each letter, then a variable that takes in the user input to change to the encrypted version.
str.translate should be the easiest way:
table = str.maketrans(
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
"cdefghijklmnopqrstuvwxyzabCDEFGHIJKLMNOPQRSTUVWXYZAB"
)
s = "Test String"
print(s.translate(table))
Output:
Vguv Uvtkpi
There's two major parts to this. First, ciphering a single letter; and second, applying that to the whole string. We'll start with the first one.
You said you had a list with the alphabet in it. Suppose, too, that we have a letter.
>>> letter = 'F'
If we want to replace that letter with the letter two spaces down in the alphabet, first we'll probably want to find the numerical value of that letter. To do that, use index:
>>> alphabet.index(letter)
5
Next, you can add the offset to it and access it in the list again:
>>> alphabet[alphabet.index(letter) + 2]
'H'
But wait, this won't work if we try doing a letter like Z, because when we add the index, we'll go off the end of the list and get an error. So we'll wrap the value around before getting the new letter:
>>> alphabet[(alphabet.index('Z') + 2) % len(alphabet)]
'B'
So now we know how to change a single letter. Python makes it easy to apply it to the whole string. First putting our single-letter version into a function:
>>> def cipher_letter(letter):
... return alphabet[(alphabet.index(letter) + 2) % len(alphabet)]
...
We can use map to apply it over a sequence. Then we get an iterable of ciphered characters, which we can join back into a string.
>>> ''.join(map(cipher_letter, 'HELLOWORLD'))
'JGNNQYQTNF'
If you want to leave characters not in alphabet in place, add a test in cipher_letter to make sure that letter in alphabet first, and if not, just return letter. Voilà.
I am trying to print the last part of a string before a certain character.
I'm not quite sure whether to use the string .split() method or string slicing or maybe something else.
Here is some code that doesn't work but I think shows the logic:
x = 'http://test.com/lalala-134'
print x['-':0] # beginning at the end of the string, return everything before '-'
Note that the number at the end will vary in size so I can't set an exact count from the end of the string.
You are looking for str.rsplit(), with a limit:
print x.rsplit('-', 1)[0]
.rsplit() searches for the splitting string from the end of input string, and the second argument limits how many times it'll split to just once.
Another option is to use str.rpartition(), which will only ever split just once:
print x.rpartition('-')[0]
For splitting just once, str.rpartition() is the faster method as well; if you need to split more than once you can only use str.rsplit().
Demo:
>>> x = 'http://test.com/lalala-134'
>>> print x.rsplit('-', 1)[0]
http://test.com/lalala
>>> 'something-with-a-lot-of-dashes'.rsplit('-', 1)[0]
'something-with-a-lot-of'
and the same with str.rpartition()
>>> print x.rpartition('-')[0]
http://test.com/lalala
>>> 'something-with-a-lot-of-dashes'.rpartition('-')[0]
'something-with-a-lot-of'
Difference between split and partition is split returns the list without delimiter and will split where ever it gets delimiter in string i.e.
x = 'http://test.com/lalala-134-431'
a,b,c = x.split(-)
print(a)
"http://test.com/lalala"
print(b)
"134"
print(c)
"431"
and partition will divide the string with only first delimiter and will only return 3 values in list
x = 'http://test.com/lalala-134-431'
a,b,c = x.partition('-')
print(a)
"http://test.com/lalala"
print(b)
"-"
print(c)
"134-431"
so as you want last value you can use rpartition it works in same way but it will find delimiter from end of string
x = 'http://test.com/lalala-134-431'
a,b,c = x.rpartition('-')
print(a)
"http://test.com/lalala-134"
print(b)
"-"
print(c)
"431"
There is a string, for example. EXAMPLE.
How can I remove the middle character, i.e., M from it? I don't need the code. I want to know:
Do strings in Python end in any special character?
Which is a better way - shifting everything right to left starting from the middle character OR creation of a new string and not copying the middle character?
In Python, strings are immutable, so you have to create a new string. You have a few options of how to create the new string. If you want to remove the 'M' wherever it appears:
newstr = oldstr.replace("M", "")
If you want to remove the central character:
midlen = len(oldstr) // 2
newstr = oldstr[:midlen] + oldstr[midlen+1:]
You asked if strings end with a special character. No, you are thinking like a C programmer. In Python, strings are stored with their length, so any byte value, including \0, can appear in a string.
To replace a specific position:
s = s[:pos] + s[(pos+1):]
To replace a specific character:
s = s.replace('M','')
This is probably the best way:
original = "EXAMPLE"
removed = original.replace("M", "")
Don't worry about shifting characters and such. Most Python code takes place on a much higher level of abstraction.
Strings are immutable. But you can convert them to a list, which is mutable, and then convert the list back to a string after you've changed it.
s = "this is a string"
l = list(s) # convert to list
l[1] = "" # "delete" letter h (the item actually still exists but is empty)
l[1:2] = [] # really delete letter h (the item is actually removed from the list)
del(l[1]) # another way to delete it
p = l.index("a") # find position of the letter "a"
del(l[p]) # delete it
s = "".join(l) # convert back to string
You can also create a new string, as others have shown, by taking everything except the character you want from the existing string.
How can I remove the middle character, i.e., M from it?
You can't, because strings in Python are immutable.
Do strings in Python end in any special character?
No. They are similar to lists of characters; the length of the list defines the length of the string, and no character acts as a terminator.
Which is a better way - shifting everything right to left starting from the middle character OR creation of a new string and not copying the middle character?
You cannot modify the existing string, so you must create a new one containing everything except the middle character.
Use the translate() method:
>>> s = 'EXAMPLE'
>>> s.translate(None, 'M')
'EXAPLE'
def kill_char(string, n): # n = position of which character you want to remove
begin = string[:n] # from beginning to n (n not included)
end = string[n+1:] # n+1 through end of string
return begin + end
print kill_char("EXAMPLE", 3) # "M" removed
I have seen this somewhere here.
card = random.choice(cards)
cardsLeft = cards.replace(card, '', 1)
How to remove one character from a string:
Here is an example where there is a stack of cards represented as characters in a string.
One of them is drawn (import random module for the random.choice() function, that picks a random character in the string).
A new string, cardsLeft, is created to hold the remaining cards given by the string function replace() where the last parameter indicates that only one "card" is to be replaced by the empty string...
On Python 2, you can use UserString.MutableString to do it in a mutable way:
>>> import UserString
>>> s = UserString.MutableString("EXAMPLE")
>>> type(s)
<class 'UserString.MutableString'>
>>> del s[3] # Delete 'M'
>>> s = str(s) # Turn it into an immutable value
>>> s
'EXAPLE'
MutableString was removed in Python 3.
Another way is with a function,
Below is a way to remove all vowels from a string, just by calling the function
def disemvowel(s):
return s.translate(None, "aeiouAEIOU")
Here's what I did to slice out the "M":
s = 'EXAMPLE'
s1 = s[:s.index('M')] + s[s.index('M')+1:]
To delete a char or a sub-string once (only the first occurrence):
main_string = main_string.replace(sub_str, replace_with, 1)
NOTE: Here 1 can be replaced with any int for the number of occurrence you want to replace.
You can simply use list comprehension.
Assume that you have the string: my name is and you want to remove character m. use the following code:
"".join([x for x in "my name is" if x is not 'm'])
If you want to delete/ignore characters in a string, and, for instance, you have this string,
"[11:L:0]"
from a web API response or something like that, like a CSV file, let's say you are using requests
import requests
udid = 123456
url = 'http://webservices.yourserver.com/action/id-' + udid
s = requests.Session()
s.verify = False
resp = s.get(url, stream=True)
content = resp.content
loop and get rid of unwanted chars:
for line in resp.iter_lines():
line = line.replace("[", "")
line = line.replace("]", "")
line = line.replace('"', "")
Optional split, and you will be able to read values individually:
listofvalues = line.split(':')
Now accessing each value is easier:
print listofvalues[0]
print listofvalues[1]
print listofvalues[2]
This will print
11
L
0
Two new string removal methods are introduced in Python 3.9+
#str.removeprefix("prefix_to_be_removed")
#str.removesuffix("suffix_to_be_removed")
s='EXAMPLE'
In this case position of 'M' is 3
s = s[:3] + s[3:].removeprefix('M')
OR
s = s[:4].removesuffix('M') + s[4:]
#output'EXAPLE'
from random import randint
def shuffle_word(word):
newWord=""
for i in range(0,len(word)):
pos=randint(0,len(word)-1)
newWord += word[pos]
word = word[:pos]+word[pos+1:]
return newWord
word = "Sarajevo"
print(shuffle_word(word))
Strings are immutable in Python so both your options mean the same thing basically.