80 lines
1.7 KiB
Python
80 lines
1.7 KiB
Python
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################## Lists ############################
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# lists are simple data structures that can hold different data types
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a = [1,2,'hallo']
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print a
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# lists are accessed by indices, starting with 0
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print a[0]
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a[0] = 5
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print a
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# lists can be indexed with slices, first index is included, the last is not
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print a[0:2]
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# if the index is ommitted, then the maximal or minimal index is taken
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print a[1:]
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print a[:1]
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# negative indices count downwards from the maximal index
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print a[:-1]
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# one can also specify steps in slices (start:stop:step)
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print a[0:3:2]
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print a[1::2]
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# if new variables are assigned to an existing list, the list is NOT copied
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b = a
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b[2] = 0
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print a
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# if you want to copy lists, use
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b = list(a)
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b[2] = 'new stuff'
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print a
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print b
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# lists of lists
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b = [1,2,3, [4,3,5]]
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print b[3][1:]
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################### Tuples #####################################
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# tuples are constant lists. They behave basically like lists but don't allow elements to be set
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b = (1,2,'hello')
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print b
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print b[::2]
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# b[2] = "test" # error!
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################### Dictionaries ###############################
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# Dictionaries are like lists that can be accessed with arbitraty
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# keys. They are initialized with curly brackets and key:value pairs
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c = {'key1':2, 3.4:'something else', 5:6}
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print c.keys()
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print c.values()
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print c.items()
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print c
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print c['key1']
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c[3.4] = 'again something else'
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print c
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# again, dictionaries are not copied
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d = c
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d[5] = 8
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print c
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############## Numerical types ##################################
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# mostly, python determines the numerical type of a number. However,
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# sometimes one needs to pay attention when dealing with integers
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a = 1
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b = 5
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print a/b
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# initialization as float or the function float(a) help
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a = 1.
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b = 5.
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print a/b
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