To create an empty list in Python, you can use two ways. First, the empty square bracket notation [] creates a new list object without any element in it. Second, the list() initializer method without an argument creates an empty list object too.

Both approaches are shown in the following code:

# Way 1 to create an empty list:

my_list = [] # Way 2 to create an empty list:

my_list = list()

Next, you’ll learn many more related Python concepts you need to know that concern creation of lists. Keep reading to keep improving your skills and answer any subsequent question you may have!

Python list() — Quick Guide

Python’s built-in list() function creates and returns a new list object. When used without an argument, it returns an empty list. When used with the optional iterable argument, it initializes the new list with the elements in the iterable.

You can create an empty list by skipping the argument:

>>> list()

[]

If you pass an iterable—such as another list, a tuple, a set, or a dictionary—you obtain a new list object with list elements obtained from the iterable:

>>> list([1, 2, 3])

[1, 2, 3]

Read More: Read our full tutorial on the Finxter blog to learn everything you need to know.

Python Create Empty List of Size

To create a list of n placeholder elements, multiply the list of a single placeholder element with n.

For example, use [None] * 5 to create a list [None, None, None, None, None] with five elements None.

You can then overwrite some elements with index assignments.

In the example, lst[2] = 42 would result in the changed list [None, None, 42, None, None].

# Create a list with n placeholder elements

n = 5

lst = [None] * n # Print the "placeholder" list:

print(lst)

# [None, None, None, None, None] # Overwrite the placeholder elements

lst[0] = 'Alice'

lst[1] = 0

lst[2] = 42

lst[3] = 12

lst[4] = 'hello'

print(lst)

# ['Alice', 0, 42, 12, 'hello']

Read More: Read our full tutorial on the Finxter blog to learn everything you need to know.

Python Create Empty List of Lists

You can create an empty list of lists do not use [[]] * n because this creates a nested list that contains the same empty list object n times which can cause problems because if you update one, all inner lists change!

To create an empty list of lists with n empty inner lists, use the list comprehension statement [[] for _ in range(n)] that creates a fresh empty list object n times.

n = 5

my_list = [[] for _ in range(n)]

print(my_list)

# [[], [], [], [], []]

List comprehension is a powerful Python feature and I’ve written a full blog tutorial on it—feel free to watch my general explainer video and read the associated blog article!

Read More: Read our full tutorial on the Finxter blog to learn everything you need to know.

Python Create Empty List and Append in Loop

Follow these three easy steps to create an empty list and append values to it in a for loop:

1. my_list = [] creates the empty list and assigns it to the name my_list.
2. for i in range(10): initializes the for loop to be repeated 10 times using loop variable i that takes on all values between 0, 1, …, 9.
3. my_list.append(i) is the loop body that appends the integer value of the loop variable i to the list.

Here’s the code example:

my_list = []

for i in range(10): my_list.append(i) print(my_list)

# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

However, a better Python one-liner alternative is using list comprehension for this:

my_list = [i for i in range(10)]

Python Create List of Empty Strings

To create a list of n empty strings, you can use the expression [''] * n because it places the same empty string literal '' into the list n times. This doesn’t cause any problems due to the fact that all list elements refer to the same empty string object because strings are immutable and cannot be modified anyways.

>>> [''] * 5

['', '', '', '', '']

>>> [''] * 20

['', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '']

Python Create Empty List of Dictionaries

To create a list of n dictionaries, each dict being empty, use the list comprehension statement [dict() for _ in range(n)] with the underscore _ as a throw-away “loop variable” and the dict() built-in dictionary creation function.

my_list = [dict() for _ in range(10)]

print(my_list)

# [{}, {}, {}, {}, {}, {}, {}, {}, {}, {}]

Note that if you update one of the dictionaries, all other dictionaries are unaffected by this because we really created n independent dictionary objects.

# update first dictionary:

my_list[0]['foo'] = 'bar' print(my_list)

# [{'foo': 'bar'}, {}, {}, {}, {}, {}, {}, {}, {}, {}]

Python Create Empty List of Class Objects

To create an empty list of class objects, you can use list comprehension statement my_list = [MyClass() for _ in range(n)] that repeats n times the creation of an empty class object MyClass and adding it to the list. You can then later change the contents of the n different MyClass objects.

class MyClass(object): pass my_list = [MyClass() for _ in range(5)] print(my_list)

# [<__main__.MyClass object at 0x000001EA45779F40>, <__main__.MyClass object at 0x000001EA47533D00>, <__main__.MyClass object at 0x000001EA475334C0>, <__main__.MyClass object at 0x000001EA4758E070>, <__main__.MyClass object at 0x000001EA4758E4F0>]

Python Create Empty List of Type

Python is a dynamic language so there is no concept of a “list of type X”. Instead of creating a list of a fixed type, simply create an empty list using [] or list() and assign it to a variable such as my_list. Using the variable, you can then fill into the existing list any data type you want!

Here we create an empty list and fill in an integer, a list, and a string—all into the same list!

my_list = []

# Alternative: my_list = list() # Add integer to list:

my_list.append(42) # Add list to list:

my_list.append([1, 2, 3]) # Add string to list:

my_list.append('hello world') # Print all contents of list:

print(my_list)

# [42, [1, 2, 3], 'hello world']

Python Create Empty List of Integers

To initialize a list with certain integers such as zeroes 0, you can either use the concise list multiplication operation [0] * n or you use list comprehension [0 for _ in range(n)].

>>> [0] * 5

[0, 0, 0, 0, 0]

>>> [0] * 10

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

>>> [42] * 5

[42, 42, 42, 42, 42]

>>> [42 for _ in range(5)]

[42, 42, 42, 42, 42]

Python Create Empty List of Tuples

To create an empty list and later add one tuple at-a-time to it, first initialize the empty list using the [] square bracket operator and then use the list.append(t) to append one tuple t at a time.

Here we add three tuples to the initially empty list:

# create empty list:

my_list = [] # append tuples

my_list.append((1, 2))

my_list.append(('alice', 'bob', 'carl'))

my_list.append(tuple()) print(my_list)

# [(1, 2), ('alice', 'bob', 'carl'), ()]

Problem Formulation

Input: You have some data in a CSV file stored in 'my_file.csv' where the first row is the header and the remaining rows are values associated to the column names in the header.

Name,Job,Age,Income
Alice,Programmer,23,110000
Bob,Executive,34,90000
Carl,Sales,45,50000

Desired Output: You want to store the data in an XML file 'my_file.xml' so that each row is represented by an XML <row> tag and each column value is associated with a specific column header tag.

<data> <row id='Alice'>

 <Name>Alice</Name>

 <Job>Programmer</Job>

 <Age>23</Age>

 <Income>110000</Income> </row>
 <row id='Bob'>

 <Name>Bob</Name>

 <Job>Executive</Job>

 <Age>34</Age>

 <Income>90000</Income> </row>

 <row id='Carl'>

 <Name>Carl</Name>

 <Job>Sales</Job>

 <Age>45</Age>

 <Income>50000</Income> </row>
</data>

Python CSV to XML – Basic Example

You can convert a CSV to an XML using the following approach:

• Read the whole CSV file into your Python script.
• Store the first row as header data that is needed to name your custom XML tags (e.g., <Name>, <Job>, <Age>, and <Income> in our example).
• Create a function convert_row() that converts each row separately to an XML representation of that row using basic string formatting.
• Iterate over the data row-wise using csv.reader() and convert each CSV row to XML using your function convert_row().

Here’s the code for copy&paste:

# Convert CSV file to XML string

import csv filename = 'my_file.csv' def convert_row(headers, row): s = f'<row id="{row[0]}">\n' for header, item in zip(headers, row): s += f' <{header}>' + f'{item}' + f'</{header}>\n' return s + '</row>' with open(filename, 'r') as f: r = csv.reader(f) headers = next® xml = '<data>\n' for row in r: xml += convert_row(headers, row) + '\n' xml += '</data>' print(xml)

Output:

<data>

<row id="Alice"> <Name>Alice</Name> <Job>Programmer</Job> <Age>23</Age> <Income>110000</Income>

</row>

<row id="Bob"> <Name>Bob</Name> <Job>Executive</Job> <Age>34</Age> <Income>90000</Income>

</row>

<row id="Carl"> <Name>Carl</Name> <Job>Sales</Job> <Age>45</Age> <Income>50000</Income>

</row>

</data>

Yay!

Note that instead of printing to the shell, you could print it to a file if this is what you need. Here’s how:

Learn More: How to print() to a file in Python?

Pandas CSV to XML

You can also use pandas instead of the csv module to read the CSV file into your Python script. Everything else remains similar—I highlighted the lines that have changed in the following code snippet:

import pandas as pd def convert_row(headers, row): s = f'<row id="{row[0]}">\n' for header, item in zip(headers, row): s += f' <{header}>' + f'{item}' + f'</{header}>\n' return s + '</row>' df = pd.read_csv("my_file.csv")

headers = df.columns.tolist()

xml = '<data>\n' for _, row in df.iterrows(): xml += convert_row(headers, row) + '\n' xml += '</data>'

print(xml)

Related CSV Conversion Tutorials

• python convert csv to json
• python convert csv to excel (xlsx)
• python convert csv to dictionary
• python convert csv to parquet
• python convert csv to list
• python convert csv to list of lists
• python convert csv to list of tuples
• python convert csv to txt
• python convert csv to dataframe
• python convert csv to list of dictionaries