Python concatenate list with examples

In this python tutorial, we will discuss the Python concatenate list, and also we will cover these below topics:

  • Python concatenate list elements with delimiter
  • Python concatenates a list of lists
  • Python concatenate a list of integers into a string
  • Python concatenate a list of tuples
  • Python concatenate a list of NumPy arrays
  • Python concatenate a list of strings with a separator
  • Python concatenate a list of dictionaries
  • Python concatenate a list of bytes
  • Python concatenate list to string
  • Python concatenates a list of arrays
  • Python concatenate a list of integers
  • Python concatenate lists without duplicates
  • Python join list of objects to string
  • Python concatenate multiple lists
  • Merge lists python unique

Python concatenate list

Here, we can see how to concatenate list in python.

  • In this example, I have taken two lists as list1, list2. The for loop is used to concatenate the list.
  • The .append is used to append the items from list2 to list1, I have used print(list1) to get the output.

Example:

list1 = [1, 3, 5, 7, 9] 
list2 = [2, 4, 6, 8, 10] 
for i in list2 : 
    list1.append(i) 
print(list1)

We can see that the two lists are appened as the output. The below screenshot shows the output.

Python concatenate list
Python concatenate list

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Python concatenate list elements with delimiter

Here, we can see how to concatenate list elements with delimiter in python?

  • In this example, I have taken as list as list = [‘1′,’2′,’3′,’4’]. The “.” delimiter is used in this example and .join() is used to concatenate the elements in the list.
  • I have used print(a) to get the output.

Example:

list = ['1','2','3','4'] 
newlist = "."
a = newlist.join(list) 
print(a) 

The below screenshot shows the concatenated list with delimiter in python as the output.

Python concatenate list elements with delimiter
Python concatenate list elements with delimiter

Python concatenates a list of lists

Now, we can see how to concatenate a list of lists in python.

  • In this example, I have taken a list as List=[[2,4],[6,8,10],[36,47,58,69]] and an empty is created.
  • To concatenate the list in an empty list for loop is used. The .append() is used to concatenate the list.
  • I have used print(empty_list) to get the output.

Example:

List=[[2,4],[6,8,10],[36,47,58,69]]
empty_list=[]
for i in List:
  for j in i:
    empty_list.append(j)
print (empty_list)

Here, we can see that concatenated list of lists is the output. You can refer to the below screenshot for the output.

Python concatenates a list of lists
Python concatenates a list of lists

This is how to concatenates a list of lists in Python.

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Python concatenate a list of integers into a string

Now, we can see how to concatenate a list of integers into a string in python.

  • In this example, I have taken a list as integer = [2,8,12]. I have used str(int) to convert a list of integers into a string.
  • To concatenate “.” delimiter, .join() method is used.
  • I have used print(string) to get the output.

Example:

integer = [2,8,12]
string = [str(int) for int in integer]
string = ".".join(string)
print(string)

The below screenshot shows the output of concatenated string with the delimiter. You can refer to the below screenshot for the output.

Python concatenate a list of integers into a string
Python concatenate a list of integers into a string

This is how to concatenate a list of integers into a string in Python.

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Python concatenate a list of tuples

Here, we can see how to concatenate a list of tuples in python

  • In this example, I have taken two tuples in a list and defined a function called tuplestring(tuple).
  • To return the string, I have used .join(tuple) for concatenation
  • The map() is used to apply for a given function to each item of an iterable of the tuple and returns a list of the results.
  • The print(list(result)) is used to get the output. The list(result) is used to check the elements present in the map.

Example:

tuples = [('x', 'y', 'z'), ('welcome', 'to', 'python', 'guides')]
def tuplestring(tuple):
   return ' '.join(tuple)
result = map(tuplestring, tuples)
print(list(result))

We can see the concatenated tuples as the output. The below screenshot for the output.

Python concatenate a list of tuples
Python concatenate a list of tuples

This is how we can concatenate a list of tuples in Python.

Python concatenate a list of NumPy arrays

Here, we can see how to concatenate a list of Numpy arrays in python (NumPy in Python)

  • In this example, I have imported a module called numpy as np.
  • I have taken two lists as a = np.array([[2, 4], [6, 8]]), b = np.array([[1, 3]])
  • I have used np.concatenate to concatenate a list.
  • The axis 0 represents rows and axis 1 represents the column and “.T” is used to transpose an array.
  • The print(c), print(d) is used to get the output.

Example:

import numpy as np
a = np.array([[2, 4], [6, 8]])
b = np.array([[1, 3]])
c= np.concatenate((a, b), axis=0)
d = np.concatenate((a, b.T), axis=1)
print(c)
print(d)

We can see the concatenated list as the output. You can refer to the below screenshot.

Python concatenate a list of NumPy arrays
Python concatenate a list of NumPy arrays

This is how to concatenate a list of NumPy arrays in Python.

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Python concatenate a list of strings with a separator

Here, we can see how to concatenate a list of strings with a separator in python

  • I have taken list as list = [‘3′,’6′,’9′,’12’]. The “-“ is the separator that I have used to concatenate the string.
  • The string.join(list) is used to concatenate the list of strings with a separator.
  • The print(string_list) is used to get the output.

Example:

list = ['3','6','9','12'] 
string = "-"
string_list = string.join(list)
print(string_list)

We can see the concatenated list with separator as the output. The below screenshot shows the output.

Python concatenate a list of strings with a separator
Python concatenate a list of strings with a separator

This is how to concatenate a list of strings with a separator in Python.

Check out Python string formatting with examples and Python concatenate tuples with examples.

Python concatenate a list of dictionaries

Here, we can see how to concatenate a list of dictionaries in python

  • In this example, I have imported a module called defaultdict from the collection. The default dict is a subclass of the dict class which returns the dictionary objects.
  • Here, I have taken two dictionaries as dict1, dict2. The for loop is used to concatenate a list of dictionaries.
  • The extend method() adds all the elements of the dictionary to the end of the list.
  • The .items returns the key-value pair of the dictionary. To get the output, I have used print(dict).

Example:

from collections import defaultdict 
dict1 = [{'roll': ['2243', '1212'], 'number': 1}, {'roll': ['14'], 'number': 2}] 
dict2 = [{'roll': ['473427'], 'number': 2}, {'roll': ['092112'], 'number': 5}] 
dictionary = defaultdict(list) 
for elem in dict1: 
	dictionary[elem['number']].extend(elem['roll']) 
for elem in dict2: 
	dictionary[elem['number']].extend(elem['roll']) 
dict = [{"roll":y, "number":x} for x, y in dictionary.items()] 
print(dict) 

We can see that the key-value pair of the dictionary is concatenated as the output. You can refer to the below screenshot for the output.

Python concatenate a list of dictionaries
Python concatenate a list of dictionaries

This is how we can concatenate a list of dictionaries in Python.

Python concatenate a list of bytes

Now, we can see how to concatenate a list of bytes in python.

  • In this example, I have taken a list of bytes. To concatenate a list of bytes, I have used the ‘-‘ separator and .join() method.

Example:

list = [b'Welcome', b'to', b'pythonguides']
print(b'- '.join(list))

The bytestring is concatenate as the output. The below screenshot shows the output.

Python concatenate a list of bytes
Python concatenate a list of bytes

This is how to concatenate a list of bytes in Python.

Python concatenate list to string

Now, we can see how to concatenate list to string in python.

  • In this example, I have taken a list as sentence = [‘welcome’,’to’,’python’,’guides’].
  • To concatenate the list to string the string = “” is used. The for loop is used for iteration.
  • The “-“ is used as the separator. The string[:-1] indicates the last element from the list.

Example:

sentence = ['welcome','to','python','guides']
string = ""
for i in sentence:
    string += str(i) + "-"
string = string[:-1]
print(string)

The below screenshot show the string is concatenated with separator as the output. You can refer to the below screenshot for the output.

Python concatenate list to string
Python concatenate list to string

In this way, we can concatenate list to string in Python.

Python concatenates a list of arrays

Here, we can see how to concatenates a list of arrays in python.

  • In this example, I have imported a module called numpy as np.
  • I have taken a list of arrays as a = [[2, 4], [6, 8]], b = [[1, 3],[9, 0]]
  • I have used np.concatenate to concatenate a list.
  • The print(c) is used to get the output.

Example:

import numpy as np
a = [[2, 4], [6, 8]]
b = [[1, 3],[9, 0]]
c= np.concatenate((a, b))
print(c)

We can see the concatenated list of array as the output. You can refer to the below screenshot for the output.

Python concatenates a list of arrays
Python concatenates a list of arrays

This is how to concatenates a list of arrays in Python.

Python concatenate a list of integers

Now, we can see how to concatenate a list of integers in python

  • In this example, I have taken two lists of integers as integers_list1, integers_list2.
  • To concatenate a list of integers an empty list is created as newlist = [].
  • The extend method() adds all the elements of the list till the end.
  • To concatenate the list on integers “+” is used.
  • The print(newlist) is used to get the output.

Example:

integers_list1 = [1,2,3]
integers_list2 = [4,5,6]
newlist = []
newlist.extend(integers_list1)
newlist.extend(integers_list2)
joinedlist = integers_list1 + integers_list2
print(newlist)

We can see the list of integers are concatenated as the output. You can refer to the below screenshot for the output.

Python concatenate a list of integers
Python concatenate a list of integers

Python concatenate lists without duplicates

Here, we can see how to concatenate lists without duplicates in python

  • In this example, I have taken two lists as list1, list2. To concatenate the list without duplicates I have used set(list2) – set(list1) to find the difference between the two lists.
  • The list and the new list are concatenated by using the “+” operator.
  • The print(new) is used to get the new list
  • The print(list) is used to get the output.

Example:

list1 = [2, 4, 6, 8]
list2 = [2, 2, 5, 5, 5, 6, 6]
new = set(list2) - set(list1)
list = list1 + list(new)
print(new)
print(list)

We can see that the list is concatenated without duplicates as the output. You can refer to the below screenshot.

Python concatenate lists without duplicates
Python concatenate lists without duplicates

This is how to concatenate lists without duplicates in Python.

Python join list of objects to string

Here, we can see how to join list of objects to string in python

  • In this example, I have defined a class called Obj.
  • The __str__(self) is the __str__ method() represents the class objects as a string and list is taken as Obj().
  • To join the list .join() is used and the str(x)is used to convert the list of objects to a string.
  • The for loop is used for iteration, I have used print(string) to get the output.

Eample:

class Obj:
	def __str__(self):
		return 'pythonguides'
list = [Obj(), Obj(), Obj()]
string = ', '.join([str(x) for x in list])
print(string)

The below screeen shot shows the output.

Python join list of objects to string
Python join list of objects to string

This is how to join list of objects to string in Python.

Python concatenate multiple lists

Now, we can see how to concatenate multiple lists in python

  • In this example, I have taken multiple lists as list1, list2, list3. The * is used to unpack the list to concatenate the multiple lists.
  • The print(list) is used to get the output.

Example:

list1 = [1, 5, 8, 70] 
list2 = [22, 26, 47, 68] 
list3 = [25, 65, 28, 78] 
list = [*list1, *list2, *list3] 
print(list) 

The below screenshot shows the output.

Python concatenate multiple lists
Python concatenate multiple lists

In this way, we can concatenate multiple lists in Python.

Merge lists python unique

Here we can see how to merge lists unique in python

  • In this example, I have taken two lists as list1, list2. To concatenate the list without duplicates I have used set(list2) – set(list1) to find the difference between the two lists.
  • The list and the new list are concatenated by using the “+” operator.
  • The print(new) is used to get the new list
  • The print(list) is used to get the output.

Example:

list1 = [1,3,5,7]
list2 = [2, 2, 5, 5, 5, 6, 6]
new = set(list2) - set(list1)
list = list1 + list(new)
print(new)
print(list)

The below screenshot shows the output.

Merge lists python unique
Merge lists python unique

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In this tutorial, we have learned about Python concatenate list, and also we have covered these topics:

  • Python concatenate list elements with delimiter
  • Python concatenates a list of lists
  • Python concatenate a list of integers into a string
  • Python concatenate a list of tuples
  • Python concatenate a list of NumPy arrays
  • Python concatenate a list of strings with a separator
  • Python concatenate a list of dictionaries
  • Python concatenate a list of bytes
  • Python concatenate list to string
  • Python concatenates a list of arrays
  • Python concatenate a list of integers
  • Python concatenate lists without duplicates
  • Python join list of objects to string
  • Python concatenate multiple lists
  • Merge lists python unique