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1.
built in string class named str, single quote or double quote both OK. use """ for multiple line string.
2.
string are immutable.
3.
zero-based indexing for accessing string with []
ex:
str = 'hello' str[1] is e
4.
don't use "len" as variable name!
5.
+ to cat two strings.
6.
a raw string :
raw = r'this\t\n and that'
print raw
7.
string slicing:
s = 'hello'
print s[1:4]
print s[1:]
print s[:]
print s[1:100]
note the last one.
8.
string methods modifies the original string.
print list.append(4) # this doesn't work
python sorting
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1.
sorted(a) doesn't change the original list.
2.
sorted() method is recommended over the old sort() method, because the former can take as input any iterable collection .
3.
sorted() string compare their ascii number lexicographically.
capital letters are smaller
4.
sort by length:
strs = ['ccc', 'aaa', 'd', 'bb']
print sorted(strs, key=len)
5.
custom key function.
strs = ['xc', 'zb', 'yd', 'wa']
def myFn(s):
return s[-1]
print sorted(strs, key = myFn)
Tuples
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1.
fixed size grouping of elements.
2.
immutable and don't change size
3.
function that returns fixed number multiple values may just return a tuple.
4.
tuple = (1,2,'hi')
print len(tuple)
print tuple[2]
tuple[2] = 'bye' # not going to work!!!!!!
tuple = (1,2, 'bye') # this works
5.
create a single element tuple, the lone element has to be followed by a comma:
tuple = ('hi',)
to distinguish a tuple from a parenthesized string.
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done
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