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string substitution for creating variable names

P: 32
In the below code, I have used 5 different variables var1xxx,...var5xxx using 5 statements. But I would like to loop over the aList elements to substitute for 1 to 5 in the variable names and hence assign the value. (Here I have shown the same element value as assigned.) Can you please let me know how to use either string substitution or string template for the following to reduce the number of lines of code and hence consice.

Thanks & Regards,
SKN

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  1. aList = [1,2,3,4,5]
  2. var1xxx = aList[0]
  3. var2xxx = aList[1]
  4. var3xxx = aList[2]
  5. var4xxx = aList[3]
  6. var5xxx = aList[4]
  7. print var1xxx,var2xxx,var3xxx,var4xxx,var5xxx
  8.  
Aug 13 '07 #1
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6 Replies


bartonc
Expert 5K+
P: 6,596
In the below code, I have used 5 different variables var1xxx,...var5xxx using 5 statements. But I would like to loop over the aList elements to substitute for 1 to 5 in the variable names and hence assign the value. (Here I have shown the same element value as assigned.) Can you please let me know how to use either string substitution or string template for the following to reduce the number of lines of code and hence consice.

Thanks & Regards,
SKN

Expand|Select|Wrap|Line Numbers
  1. aList = [1,2,3,4,5]
  2. var1xxx = aList[0]
  3. var2xxx = aList[1]
  4. var3xxx = aList[2]
  5. var4xxx = aList[3]
  6. var5xxx = aList[4]
  7. print var1xxx,var2xxx,var3xxx,var4xxx,var5xxx
  8.  
That's a fun one! I really liked writing this:
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  1. >>> aList = [1,2,3,4,5]
  2. >>> for i, value in enumerate(aList):
  3. ...     exec("var%dxxx = value" %(i+1))
  4. ...     
  5. >>> var1xxx
  6. 1
  7. >>> 
Aug 13 '07 #2

P: 32
That's a fun one! I really liked writing this:
Expand|Select|Wrap|Line Numbers
  1. >>> aList = [1,2,3,4,5]
  2. >>> for i, value in enumerate(aList):
  3. ...     exec("var%dxxx = value" %(i+1))
  4. ...     
  5. >>> var1xxx
  6. 1
  7. >>> 
Thanks Bartonc. If aList has ['abc,'def','ghi'] in place of integers, then how to do that. Assuming that we have string substitution on right side variables also.
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  1. aList = ['abc','def','hij']
  2. aabcList = [1,2,3]
  3. adefList = [3,4,5]
  4. ahijList = [4,5,6]
  5. varabcxxx = aabcList[0]
  6. vardefxxx = adefList[0]
  7. varhijxxx = ahijList[0]
  8. print varabcxxx,vardefxxx,varhijxxx
  9.  
Thanks
SKN
Aug 13 '07 #3

bvdet
Expert Mod 2.5K+
P: 2,851
Thanks Bartonc. If aList has ['abc,'def','ghi'] in place of integers, then how to do that. Assuming that we have string substitution on right side variables also.
Expand|Select|Wrap|Line Numbers
  1. aList = ['abc','def','hij']
  2. aabcList = [1,2,3]
  3. adefList = [3,4,5]
  4. ahijList = [4,5,6]
  5. varabcxxx = aabcList[0]
  6. vardefxxx = adefList[0]
  7. varhijxxx = ahijList[0]
  8. print varabcxxx,vardefxxx,varhijxxx
  9.  
Thanks
SKN
Here is one way:
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  1. >>> aList = ['abc','def','hij']
  2. >>> pre = 'var'
  3. >>> suf = 'xxx'
  4. >>> data = [[1,2,3], [3,4,5], [4,5,6]]
  5. >>> def var_dict(p,iList,s,data):
  6. ...     dd = {}
  7. ...     for i, item in enumerate(iList):
  8. ...         dd['a%sList' % item] = data[i]
  9. ...         dd['%s%s%s' % (p,item,s)] = data[i][0]
  10. ...     globals().update(dd)
  11. ...     return dd
  12. ... 
  13. >>> dd = var_dict(pre,aList,suf,data)
  14. >>> aabcList
  15. [1, 2, 3]
  16. >>> varabcxxx
  17. 1
  18. >>>
I did not need to return the dictionary or assign the function call to a variable. globals().update() assigns the values to the variable names in the global namespace of the module.
Aug 13 '07 #4

P: 32
Here is one way:
Expand|Select|Wrap|Line Numbers
  1. >>> aList = ['abc','def','hij']
  2. >>> pre = 'var'
  3. >>> suf = 'xxx'
  4. >>> data = [[1,2,3], [3,4,5], [4,5,6]]
  5. >>> def var_dict(p,iList,s,data):
  6. ...     dd = {}
  7. ...     for i, item in enumerate(iList):
  8. ...         dd['a%sList' % item] = data[i]
  9. ...         dd['%s%s%s' % (p,item,s)] = data[i][0]
  10. ...     globals().update(dd)
  11. ...     return dd
  12. ... 
  13. >>> dd = var_dict(pre,aList,suf,data)
  14. >>> aabcList
  15. [1, 2, 3]
  16. >>> varabcxxx
  17. 1
  18. >>>
I did not need to return the dictionary or assign the function call to a variable. globals().update() assigns the values to the variable names in the global namespace of the module.
Thanks BV. Is it possible to use a dynamic list defined. I mean instead of defining "data" can we have aabcList[0] defined inside using the same substitute "abc" string in both left and right hand side of the assignment statement.


Regards,
SKN
Aug 14 '07 #5

bvdet
Expert Mod 2.5K+
P: 2,851
Thanks BV. Is it possible to use a dynamic list defined. I mean instead of defining "data" can we have aabcList[0] defined inside using the same substitute "abc" string in both left and right hand side of the assignment statement.


Regards,
SKN
This can be done similar to what Barton proposed using exec() and eval(). Keeping with the dictionary approach:
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  1. aList = ['abc','def','hij']
  2.  
  3. dd1 = dict(zip(['a%sList' % item for item in aList], [[11,12,13], [13,14,15], [14,15,16]]))
  4. for item in aList:
  5.     dd1['v%sxxx' % item] = dd1['a%sList' % item][0]
  6. globals().update(dd1)
Aug 14 '07 #6

P: 32
Thanks a bunch, BV. Which approach is efficient? Dictionary approach or using exec() and eval().


Regards,
SKN
Aug 14 '07 #7

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