# In Python, how do I convert all of the items in a list to floats?

PythonListCasting## Python Problem Overview

I have a script which reads a text file, pulls decimal numbers out of it as strings and places them into a list.

So I have this list:

```
my_list = ['0.49', '0.54', '0.54', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54']
```

How do I convert each of the values in the list from a string to a float?

I have tried:

```
for item in my_list:
float(item)
```

But this doesn't seem to work for me.

## Python Solutions

## Solution 1 - Python

```
[float(i) for i in lst]
```

to be precise, it creates a new list with float values. Unlike the `map`

approach it will work in py3k.

## Solution 2 - Python

`map(float, mylist)`

should do it.

(In Python 3, map ceases to return a list object, so if you want a new list and not just something to iterate over, you either need `list(map(float, mylist)`

- or use SilentGhost's answer which arguably is more pythonic.)

## Solution 3 - Python

This would be an other method (without using any loop!):

```
import numpy as np
list(np.float_(list_name))
```

## Solution 4 - Python

`float(item)`

do the right thing: it converts its argument to float and and return it, but it doesn't change argument in-place. A simple fix for your code is:

```
new_list = []
for item in list:
new_list.append(float(item))
```

The same code can written shorter using list comprehension: `new_list = [float(i) for i in list]`

To change list in-place:

```
for index, item in enumerate(list):
list[index] = float(item)
```

BTW, avoid using `list`

for your variables, since it masquerades built-in function with the same name.

## Solution 5 - Python

you can even do this by numpy

```
import numpy as np
np.array(your_list,dtype=float)
```

this return np array of your list as float

you also can set 'dtype' as int

## Solution 6 - Python

You can use the `map()`

function to convert the list directly to `floats`

:

```
float_list = map(float, list)
```

## Solution 7 - Python

You can use numpy to convert a list directly to a floating array or matrix.

```
import numpy as np
list_ex = [1, 0] # This a list
list_int = np.array(list_ex) # This is a numpy integer array
```

If you want to convert the integer array to a floating array then add 0. to it

```
list_float = np.array(list_ex) + 0. # This is a numpy floating array
```

## Solution 8 - Python

you can use numpy to avoid looping:

```
import numpy as np
list(np.array(my_list).astype(float)
```

## Solution 9 - Python

This is how I would do it.

```
my_list = ['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54',
'0.54', '0.54', '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54',
'0.55', '0.55', '0.54']
print type(my_list[0]) # prints <type 'str'>
my_list = [float(i) for i in my_list]
print type(my_list[0]) # prints <type 'float'>
```

## Solution 10 - Python

```
import numpy as np
my_list = ['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54', '0.54', '0.54', '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54',
'0.55', '0.55', '0.54']
print(type(my_list), type(my_list[0]))
# <class 'list'> <class 'str'>
```

which displays the type as a list of strings. You can convert this list to an array of floats simultaneously using numpy:

```
my_list = np.array(my_list).astype(np.float)
print(type(my_list), type(my_list[0]))
# <class 'numpy.ndarray'> <class 'numpy.float64'>
```

## Solution 11 - Python

I have solve this problem in my program using:

```
number_input = float("{:.1f}".format(float(input())))
list.append(number_input)
```

## Solution 12 - Python

I had to extract numbers first from a list of float strings:

```
df4['sscore'] = df4['simscore'].str.findall('\d+\.\d+')
```

then each convert to a float:

```
ad=[]
for z in range(len(df4)):
ad.append([float(i) for i in df4['sscore'][z]])
```

in the end assign all floats to a dataframe as float64:

```
df4['fscore'] = np.array(ad,dtype=float)
```

## Solution 13 - Python

```
for i in range(len(list)): list[i]=float(list[i])
```