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if elif else
They are the base elements to create conditional block of instructions. elif creates a new condition inside the previous if else branch. Use several elif simulates the command case or switch found in other language.Examples:
| Without elif | With elif |
| >>> if a>0: … print "Positive number" … else : … if a== 0: … print "Zero" … else : … print "Negative number " … | >>> if a>0: … print "Positive number" … elif a==0: … print "Zero" … else : … print "Negative number" … |
for
All elements in a list can be manipulated one by one with this command. If a loop changes the list, a copy of the list must be used to iterate. To do it, add at the end of the variable's name the characters [:] (a colon between square brackets).Examples:
| Normal iteration | Iteration with copy to modify original |
| >>> list=[ 1,3,5,7 ] >>> for A in list : … print A … 1 2 3 4 >>> print list [1, 2, 3, 4] | >>> list=[ 1,2,3,4 ] >>> for A in list[:]: … print A … list.append(A+4) … 1 2 3 4 >>> print list [1, 2, 3, 4, 5, 6, 7, 8 ] |
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