Python Pocket Reference, 3rd Edition

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Python Pocket Reference

Sequence Operation Notes

Indexing: S[i]

• Fetches components at offsets (first item is at offset 0).

• Negative indexes mean to count backward from the end.

•

S[0] fetches the first item.

•

S[-2] fetches the second-to-last item (S[len(S) - 2]).

Slicing: S[i:j]

• Extracts contiguous sections of a sequence.

• Slice boundaries default to 0 and sequence length.

•

S[1:3] fetches from offsets 1 up to, but not including, 3.

•

S[1:] fetches from offsets 1 through the end (length-1).

•

S[:-1] fetches from offsets 0 up to, but not including, the

last item.

•

S[:]

makes a top-level (shallow) copy of sequence object

S

.

• Slice assignment is similar to deleting and then inserting.

X << N, X >> N Bitwise left-shift, right-

shift (integers).

__lshift__,

__rshift__

~X

Bitwise invert (integers). __invert__

X ** Y X

to the power Y. __pow__

abs(X)

Absolute value. __abs__

int(X)

Convert to integer. __int__

long(X)

Convert to long. __long__

float(X)

Convert to float. __float__

complex(X),

complex(re,im)

Make a complex value. __complex__

divmod(X, Y)

Tuple: (X/Y, X%Y). __divmod__

pow(X, Y [,Z])

Raise to a power. __pow__

Table 6. Numeric operations (all number types) (continued)

Operation Description Class method