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October 13, 2018 12:10
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Python list transformations showing various aspects of the Python 2 and 3 language evolvements
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# Links the documentation are Python 2, though everything works in Python 3 as well. | |
x = [1,2,3,4,5,11] | |
print("x: ", repr(x)) | |
y = ['01','02','03','04','05','11'] | |
print("y: ", repr(y)) | |
# List comprehension https://docs.python.org/2/tutorial/datastructures.html#list-comprehensions | |
# ... using `str.format()` (Python >= 2.6): https://docs.python.org/2/library/stdtypes.html#str.format and https://docs.python.org/2/library/string.html#formatstrings | |
y = ["{0:0>2}".format(v) for v in x] | |
print("y: ", repr(y)) | |
# ... using the traditional `%` formatting operator (Python < 2.6): https://docs.python.org/2/library/stdtypes.html#string-formatting | |
y = ["%02d" % v for v in x] | |
print("y: ", repr(y)) | |
# ... using the format()` function (Python >= 2.6): https://docs.python.org/2/library/functions.html#format and https://docs.python.org/2/library/string.html#formatstrings | |
# this omits the "{0:...}" ceremony from the positional #0 parameter | |
y = [format(v, "0>2") for v in x] | |
print("y: ", repr(y)) | |
# Note that for new style format strings, the positional argument (to specify argument #0) is optional (Python >= 2.7) https://docs.python.org/2/library/string.html#formatstrings | |
y = ["{:0>2}".format(v) for v in x] | |
print("y: ", repr(y)) | |
# Using `lambda` | |
# ... Python < 3 return a list | |
y = map(lambda v: "%02d" %v, x) | |
print("y: ", repr(y)) | |
# ... Python >= 3 return a map object to iterate over https://stackoverflow.com/questions/1303347/getting-a-map-to-return-a-list-in-python-3-x/1303354#1303354 | |
y = list(map(lambda v: "%02d" %v, x)) | |
print("y: ", repr(y)) |
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