A substring is a portion of a string. There are several methods in Python for creating a substring and checking if a substring exists in a string, the index of a substring, and more. Let’s take a look at some substring operations.
Slicing
You can extract a substring from a string by slicing with indices that correspond to your substring.
Syntax:
gvn_string[start:stop:step]
Parameters
- start: Slicing begins at this index of the list.
- stop: The index of the list at which slicing ends.
- step: It allows you to select the nth item from start to stop. A number indicating the step of slicing. The default value is 1.
Python Program to Get the substring from a given string using list slicing
Method #1: Slicing with start and stop values
Approach:
- Give the string as static input and store it in a variable.
- Print the given string
- Create a substring from the start of the string till the required index you want
- Create a substring from the end of the string
- Print the substring from the start of the string using slicing.
- Here printing characters from 0 to 2(excluding the last index).
- Print the substring from the end of the string using slicing
- Here printing characters from 4 to the entire string.
- The Exit of the Program.
Below is the implementation:
# Give the string as static input and store it in a variable.
gvn_str = 'hellothisispythonprograms'
# Print the given string
print("The given string = ", gvn_str)
# create a substring from the start of string till the required index you want
substr_frm_start = gvn_str[:3]
# create a substring from the end of string
substr_frm_end = gvn_str[4:]
# Print the substring from the starting of the string using slicing
# here printing charcters from 0 to 2(excluding the last index)
print("The substring from the starting of the string = ", substr_frm_start)
# Print the substring from the end of the string using slicing
# here printing characters from 4 to entire string
print("The substring from the end of the string = ", substr_frm_end)Output:
The given string = hellothisispythonprograms The substring from the starting of the string = hel The substring from the end of the string = othisispythonprograms
Method #2: Slicing with a step value
Approach:
- Give the string as static input and store it in a variable.
- Print the given string
- Get the substring by taking step value as 3 to the slicing
- Get the alternative character substring by taking step value as 2
- Print the substring from the start of the given string with 3 step
- Print the substring from the given string with alternate characters(step=2).
- The Exit of the Program.
Below is the implementation:
# Give the string as static input and store it in a variable.
gvn_str = 'hellothisispythonprograms'
# Print the given string
print("The given string = ", gvn_str)
# Get the substring by taking step value as 3 to the slicing
substr_withstep3 = gvn_str[::3]
# Get the alternative character substring by taking step value as 2
substr_withstep2 = gvn_str[::2]
# print the substring from the start of the given string with 3 step
print("The substring from the start of the given string with 3 step = ", substr_withstep3)
# print the substring from the given string with alternate characters(step=2)
print("The substring from the given string with alternate characters(step=2)= ", substr_withstep2)Output:
The given string = hellothisispythonprograms The substring from the start of the given string with 3 step = hlhiyorrs The substring from the given string with alternate characters(step=2)= hlohssyhnrgas
Method #3: Slicing with start, stop and step values
Approach:
- Give the string as static input and store it in a variable.
- Print the given string
- Slice from 2nd index to 7 index with alternate characters(because we used step value as 2)
- Print the resulting substring.
- The Exit of the Program.
Below is the implementation:
# Give the string as static input and store it in a variable.
gvn_str = 'hellothisispythonprograms'
# Print the given string
print("The given string = ", gvn_str)
# Slice from 2nd index to 7 index with alternate characters(because we used step value as 2)
sub_string = gvn_str[2:7:2]
# Print the result substring
print ("The result substring = ", sub_string)
Output:
The given string = hellothisispythonprograms The result substring = loh
Method #4: Slicing with start, stop and step values (User Input)
Approach:
- Give the string as user input using the input() function and store it in a variable.
- Print the given string
- Give the start value as user input using the int(), input() functions and store it in another variable (here int() converts to an integer datatype)
- Give the end value as user input using the int(), input() functions and store it in another variable
- Give the step value as user input using the int(), input() functions
and store it in another variable - Slice the given string based on the above-given start, end and step values and store it in another variable
- Print the resulting substring.
- The Exit of the Program.
Below is the implementation:
# Give the string as user input using the input() function and store it in a variable.
gvn_str = input("Give some random string = ")
# Print the given string
print("The given string = ", gvn_str)
# Give the start value as user input using the int(), input() functions
# and store it in another variable (here int() converts to an integer datatype)
gvn_startval = int(input("Give some random start value = "))
# Give the end value as user input using the int(), input() functions
# and store it in another variable
gvn_endval = int(input("Give some random end value = "))
# Give the step value as user input using the int(), input() functions
# and store it in another variable
gvn_step = int(input("Give some random step value = "))
# Slice the given string based on the above given start, end and step values
# and store it in another variable
sub_string = gvn_str[gvn_startval:gvn_endval:gvn_step]
# Print the result substring
print ("The result substring = ", sub_string)Output:
Give some random string = good morning python programs The given string = good morning python programs Give some random start value = 1 Give some random end value = 15 Give some random step value = 2 The result substring = odmrigp
Explanation:
Here the string "good morning python programs" is sliced from the start index=1(o) to the end index 15(t) with a step value =2 i.e, it prints alternative characters
Method #5: Slicing with a step value (User Input)
Approach:
- Give the string as user input using the input() function and store it in a variable.
- Print the given string
- Give the step value as user input using the int(), and input() functions and store it in another variable (here int() function converts to an integer datatype).
- Get the substring by taking the given step value to perform slicing.
- Print the substring from the input string based on the given step value.
- The Exit of the Program.
Below is the implementation:
# Give the string as user input using the input() function and store it in a variable.
gvn_str = input("Give some random string = ")
# Print the given string
print("The given string = ", gvn_str)
# Give the step value as user input using the int(), input() functions
# and store it in another variable (here int() function converts to an integer datatype)
gvn_step = int(input("Give some random step value = "))
# Get the substring by taking the given step value to perform slicing
substr_withstep = gvn_str[::gvn_step]
# print the substring from the input string based on the given step value
print("The substring from the input string based on the given step value = ", substr_withstep)
Output:
Give some random string = hellothisispythonprograms The given string = hellothisispythonprograms Give some random step value = 2 The substring from the input string based on the given step value = hlohssyhnrgas