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Variables and References in Python
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"TAGAGAATTCTA” Objects s Names References >>> s = “TAGAGAATTCTA” >>>
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"TAGAGAATTCTA" "GAAT" Objects s t Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>>
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"TAGAGAATTCTA" "GAAT" 4 Objects s t i Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>> i = s.find(t) >>> print i 4 >>> Strings have a “find” method
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"TAGAGAATTCTA" "GAAT" 4 Objects s t i Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>> i = s.find(t) >>> print i 4 >>> t = s >>>
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"TAGAGAATTCTA" 4 Objects s t i Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>> i = s.find(t) >>> print i 4 >>> t = s >>>
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"TAGAGAATTCTA" 4 Objects s t i Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>> i = s.find(t) >>> print i 4 >>> t = s >>> a Traceback (most recent call last): File " ", line 1, in ? NameError: name 'a' is not defined >>>
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"TAGAGAATTCTA" "GA" 4 Objects s t i Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>> i = s.find(t) >>> print i 4 >>> t = s >>> a Traceback (most recent call last): File " ", line 1, in ? NameError: name 'a' is not defined >>> s = “GA” >>> print t TAGAGAATTCTA >>>
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"GA" 4 Objects s i Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>> i = s.find(t) >>> print i 4 >>> t = s >>> a Traceback (most recent call last): File " ", line 1, in ? NameError: name 'a' is not defined >>> s = “GA” >>> print t TAGAGAATTCTA >>> del t >>>
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"GA" 4 Objects s i Names References >>> s = “TAGAGAATTCTA” >>> t = “GAAT” >>> i = s.find(t) >>> print i 4 >>> t = s >>> print a Traceback (most recent call last): File " ", line 1, in ? NameError: name 'a' is not defined >>> s = “GA” >>> print t TAGAGAATTCTA >>> del t >>> print t Traceback (most recent call last): File " ", line 1, in ? NameError: name 't' is not defined >>>
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[2, 4] Objects L1 Names References >>> L1 = [2, 4] >>>
![[2, 4] Objects L1 Names References >>> L1 = [2, 4] >>>](http://images.slideplayer.com./9/2662687/slides/slide_11.jpg "[2, 4] Objects L1 Names References >>> L1 = [2, 4] >>>")
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[2, 4, 5] Objects L1 Names References >>> L1 = [2, 4] >>> L1.append(5) >>>
![[2, 4, 5] Objects L1 Names References >>> L1 = [2, 4] >>> L1.append(5) >>>](http://images.slideplayer.com./9/2662687/slides/slide_12.jpg "[2, 4, 5] Objects L1 Names References >>> L1 = [2, 4] >>> L1.append(5) >>>")
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[2, 4, 5] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>>
![[2, 4, 5] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>>](http://images.slideplayer.com./9/2662687/slides/slide_13.jpg "[2, 4, 5] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>>")
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[2, 4, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>>
![[2, 4, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>>](http://images.slideplayer.com./9/2662687/slides/slide_14.jpg "[2, 4, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>>")
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[2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>>
![[2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>>](http://images.slideplayer.com./9/2662687/slides/slide_15.jpg "[2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>>")
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[2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>> L2 = L1[:] >>> L1 == L2 True >>>
![[2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>> L2 = L1[:] >>> L1 == L2 True >>>](http://images.slideplayer.com./9/2662687/slides/slide_16.jpg "[2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>> L2 = L1[:] >>> L1 == L2 True >>>")
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[7, 5, 2] [2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>> L2 = L1[:] >>> L1 == L2 True >>> L1.reverse() >>> L1 == L2 False >>>
![[7, 5, 2] [2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>> L2 = L1[:] >>> L1 == L2 True >>> L1.reverse() >>> L1 == L2 False >>>](http://images.slideplayer.com./9/2662687/slides/slide_17.jpg "[7, 5, 2] [2, 5, 7] Objects L1 L2 Names References >>> L1 = [2, 4] >>> L1.append(5) >>> L2 = L1 >>> L2.append(7) >>> print L1 [2, 4, 5, 7] >>> print L2 [2, 4, 5, 7] >>> del L2[1] >>> L2 = L1[:] >>> L1 == L2 True >>> L1.reverse() >>> L1 == L2 False >>>")
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