List comprehension is how I'd do it, it's the "Pythonic" way. The following transcript shows how to convert a list to all upper case then back to lower:
pax@paxbox7:~$ python3
Python 3.5.2 (default, Nov 17 2016, 17:05:23)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> x = ["one", "two", "three"] ; x
['one', 'two', 'three']
>>> x = [element.upper() for element in x] ; x
['ONE', 'TWO', 'THREE']
>>> x = [element.lower() for element in x] ; x
['one', 'two', 'three']
>>> map(str.lower,["A","B","C"])
['a', 'b', 'c']
a student asking, another student with the same problem answering :))
fruits=['orange', 'grape', 'kiwi', 'apple', 'mango', 'fig', 'lemon']
newList = []
for fruit in fruits:
newList.append(fruit.upper())
print(newList)
If you are trying to convert all string to lowercase in the list, You can use pandas :
import pandas as pd
data = ['Study', 'Insights']
pd_d = list(pd.Series(data).str.lower())
output:
['study', 'insights']
You could try using:
my_list = ['india', 'america', 'china', 'korea']
def capitalize_list(item):
return item.upper()
print(list(map(capitalize_list, my_list)))
A much simpler version of the top answer is given here by @Amorpheuses.
With a list of values in val:
valsLower = [item.lower() for item in vals]
This worked well for me with an f = open() text source.
If your purpose is to matching with another string by converting in one pass, you can use str.casefold() as well.
This is useful when you have non-ascii characters and matching with ascii versions(eg: maße vs masse).Though str.lower or str.upper fails in such cases, str.casefold() will pass.
This is available in Python 3 and the idea is discussed in detail with the answer https://stackoverflow.com/a/31599276/4848659.
>>>str="Hello World";
>>>print(str.lower());
hello world
>>>print(str.upper());
HELLO WOLRD
>>>print(str.casefold());
hello world
mylist = ['Mixed Case One', 'Mixed Case Two', 'Mixed Three']
print(list(map(lambda x: x.lower(), mylist)))
print(list(map(lambda x: x.upper(), mylist)))
Python3.6.8
In [1]: a = 'which option is the fastest'
In [2]: %%timeit
...: ''.join(a).upper()
762 ns ± 11.4 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
In [3]: %%timeit
...: map(lambda x:x.upper(), a)
209 ns ± 5.73 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
In [4]: %%timeit
...: map(str.upper, [i for i in a])
1.18 µs ± 11.3 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
In [5]: %%timeit
...: [i.upper() for i in a]
3.2 µs ± 64.1 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
If you need a string or list as the output and not an iterator (this is for Python3), compare ''.join(string).upper() option to this:
In [10]: %%timeit
...: [i for i in map(lambda x:x.upper(), a)]
4.32 µs ± 112 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
For this sample the comprehension is fastest
$ python -m timeit -s 's=["one","two","three"]*1000' '[x.upper for x in s]' 1000 loops, best of 3: 809 usec per loop $ python -m timeit -s 's=["one","two","three"]*1000' 'map(str.upper,s)' 1000 loops, best of 3: 1.12 msec per loop $ python -m timeit -s 's=["one","two","three"]*1000' 'map(lambda x:x.upper(),s)' 1000 loops, best of 3: 1.77 msec per loop
Besides being easier to read (for many people), list comprehensions win the speed race, too:
$ python2.6 -m timeit '[x.lower() for x in ["A","B","C"]]'
1000000 loops, best of 3: 1.03 usec per loop
$ python2.6 -m timeit '[x.upper() for x in ["a","b","c"]]'
1000000 loops, best of 3: 1.04 usec per loop
$ python2.6 -m timeit 'map(str.lower,["A","B","C"])'
1000000 loops, best of 3: 1.44 usec per loop
$ python2.6 -m timeit 'map(str.upper,["a","b","c"])'
1000000 loops, best of 3: 1.44 usec per loop
$ python2.6 -m timeit 'map(lambda x:x.lower(),["A","B","C"])'
1000000 loops, best of 3: 1.87 usec per loop
$ python2.6 -m timeit 'map(lambda x:x.upper(),["a","b","c"])'
1000000 loops, best of 3: 1.87 usec per loop
Solution:
>>> s = []
>>> p = ['This', 'That', 'There', 'is', 'apple']
>>> [s.append(i.lower()) if not i.islower() else s.append(i) for i in p]
>>> s
>>> ['this', 'that', 'there', 'is','apple']
This solution will create a separate list containing the lowercase items, regardless of their original case. If the original case is upper then the list s will contain lowercase of the respective item in list p. If the original case of the list item is already lowercase in list p then the list s will retain the item's case and keep it in lowercase. Now you can use list s instead of list p.
Source: Stackoverflow.com