This article shows how to convert list of string to either int or float.
Contents
- convert 1D list using "for statement"
- convert 1D list using "map( ) function"
- convert 2D list using "for statement"
- convert 2D list using "map( ) function" and "comprehension"
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convert 1D list using "for statement"
In the beginning, I show how to convert 1D list using "for statement".
Data type conversion is described as follows.
How to write
convert to int : int(value)
convert to float : float(value)
convert to string : str(value)
This is an example code.
Using "for statement", strings in 1D list are converted to int type.
list_1D = ['11', '12', '13', '14']
list_1D_int = []
for data in list_1D :
list_1D_int.append(int(data))
print(list(list_1D_int))
# [11, 12, 13, 14]> for data in list_1D :
The elements are taken out of the list one by one.
> list_1D_int.append(int(data))
The elements converted to int type are added to the list "list_1D_int".
This is an example code to convert to float type.
list_1D = ['1.1', '1.2', '1.3', '1.4']
list_1D_float = []
for data in list_1D :
list_1D_float.append(float(data))
print(list(list_1D_float))
# [1.1, 1.2, 1.3, 1.4]> list_1D_float.append(float(data))
The elements converted to float type are added to the list "list_1D_float".
As I show in the next section, the map( ) function can be used for a more concise description
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convert 1D list using "map( ) function"
I show how to convert 1D list using "map( ) function".
By using map(), function can be applied to all elements of the iterable object( list, tuple, etc.).
This function can be a built-in function, a user-defined function, or a lambda function.
How to write
map( Function, iterable object )
This is an example code to convert to int type.
list_1D = ['11', '12', '13', '14']
list_1D_int = map(int, list_1D)
print(list_1D_int)
# <map object at 0x0000026AB7447C88>
print(list(list_1D_int))
# [11, 12, 13, 14]The map( ) function returns a map object.
The elements cannot be checked by print( ).
Therefore, list( ) function is used to convert the map object to the list.
How to use of map( ) function is explained in this article.
This is an example code to convert to float type.
list_1D = ['1.1', '1.2', '1.3', '1.4']
list_1D_float = map(float, list_1D)
print(list_1D_float)
# <map object at 0x0000026AB7447C88>
print(list(list_1D_float))
# [1.1, 1.2, 1.3, 1.4]> list_1D_float = map(float, list_1D)
By using float( ) function, strings in list are converted to float type.
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convert 2D list using "for statement"
I show how to convert 2D list using "for statement".
This is an example code to convert to int type.
list_2D = [
['11', '12', '13', '14'],
['21', '22', '23', '24'],
['31', '32', '33', '34']
]
list_2D_int = []
for row in list_2D:
row_int = []
for data in row:
row_int.append(int(data))
list_2D_int.append(row_int)
print(list_2D_int)
# [[11, 12, 13, 14], [21, 22, 23, 24], [31, 32, 33, 34]]
print(type(list_2D_int[0][0]))
# <class 'int'>> for row in list_2D :
The elements are taken out of the list line by line.
> for data in row:
The elements are taken one by one from the row data.
> row_int.append(int(data))
The elements converted to int type are added to the list "row_int".
> list_2D_int.append(row_int)
The list "row_int", which contains one row of elements, is added to "list_2D_str".
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convert 2D list using "map( ) function" and "comprehension"
I show how to convert 2D list using "map( ) function" and "comprehension".
This is an example code to convert to int type.
list_2D = [
['11', '12', '13', '14'],
['21', '22', '23', '24'],
['31', '32', '33', '34']
]
list_2D_int = [list(map(int, row)) for row in list_2D]
print(list_2D_int)
# [[11, 12, 13, 14], [21, 22, 23, 24], [31, 32, 33, 34]]> list_2D_int = [list(map(int, row)) for row in list_2D]
The elements are taken from the list "list_2D" line by line, passed to map( ) function.
How to use of comprehension is explained in this article.
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