Creating variables in loop and initialize them in Python

Question

I have got 10 parameters to initialize. Following a convention, they are named as a_true, b_true etc. They are not a list or array but independent variables.They need to be initialized from an array of length 1X10.

I intend to do something like this which I know has got its shortcomings:

param=[34,65,...,234] # Contains initialization values
var=['a','b','c','d','e','f','g','h','i','j']
gvalues=[] # Array intended to contain variable names
k=0
for i in var:
    gvalues.append(var[k]+'_true')
    k+=1

This creates an array of elements like a_true, b_true etc. I want to take them as variables rather than as elements of an array and finally initialize them with the values from param. Any possibilities? Sorry from a newbie if it seems trivial.

Output_intended:

[a_true, b_true, ..., j_true]=[34, 65, ... , 234]

@user3440489 show the output what you want. you are not clear yet. Better use i+'_true' in for loop remove k. — Vishnu Upadhyay
– Vishnu Upadhyay, Commented Oct 31, 2014 at 6:29
Just a note: You are probably better off making them into a list or dict or other structure, instead of using separate variables. — BrenBarn
– BrenBarn, Commented Oct 31, 2014 at 6:54

Chris Martin · Accepted Answer · 2014-10-31 06:40:27Z

6

You can use locals() and globals() to dynamically assign variables.

>>> param = range(10)
>>> var = 'abcdefghij'
>>> locals().update({'{}_true'.format(k): v for k, v in zip(var, param)})
>>> c_true
2
>>> f_true
5

edited Oct 31, 2014 at 6:40

answered Oct 31, 2014 at 6:31

Chris Martin

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Community · Accepted Answer · 2017-05-23 11:48:21Z

2

It was already discussed here:

Using a string variable as a variable name

In particular, something like this should work:

for k, v in zip(gvalues, params):
    exec('%s = %s' % (k, v))

edited May 23, 2017 at 11:48

CommunityBot

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answered Oct 31, 2014 at 6:32

Ishamael

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Comments

CyanogenCX · Accepted Answer · 2014-10-31 06:35:43Z

0

You can try using a dictionary, with the keys being a_true, ect and the values being the numbers.

dict={}

dict['a_true']=35

etc

or you can do the whole thing in a loop.

answered Oct 31, 2014 at 6:35

CyanogenCX

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user3378649 · Accepted Answer · 2014-10-31 06:36:14Z

-1

You can through list of letters and concatenate every letter with '_true'

import string

gvalues =[x+'_true' for x in string.ascii_lowercase]
print gvalues

Output:

['a_true', 'b_true', 'c_true', 'd_true', 'e_true', 'f_true', 'g_true', 'h_true', 'i_true', 'j_true', 'k_true', 'l_true', 'm_true', 'n_true', 'o_true', 'p_true', 'q_true', 'r_true', 's_true', 't_true', 'u_true', 'v_true', 'w_true', 'x_true', 'y_true', 'z_true']

In case you need to concatenate it with all letter (Upper case + Lower case.)

import string

gvalues =[x+'_true' for x in string.ascii_letters]
print gvalues

That would give you:

['a_true', 'b_true', 'c_true', 'd_true', 'e_true', 'f_true', 'g_true', 'h_true', 'i_true', 'j_true', 'k_true', 'l_true', 'm_true', 'n_true', 'o_true', 'p_true', 'q_true', 'r_true', 's_true', 't_true', 'u_true', 'v_true', 'w_true', 'x_true', 'y_true', 'z_true', 'A_true', 'B_true', 'C_true', 'D_true', 'E_true', 'F_true', 'G_true', 'H_true', 'I_true', 'J_true', 'K_true', 'L_true', 'M_true', 'N_true', 'O_true', 'P_true', 'Q_true', 'R_true', 'S_true', 'T_true', 'U_true', 'V_true', 'W_true', 'X_true', 'Y_true', 'Z_true']

UPDATE

If you wanna create variable with name 'a_true'. This is not the best to do it. However, you can use Dictionaries. It's a way to map variable using keys to get values.

In this example. we add 'a_true' as a key, to get a value.

d= {'a_true':1, 'b_true':2, 'c_true':3, 'd_true':3}

print d['a_true']

would give you: 1

print d['b_true']

would give you: 2

edited Oct 31, 2014 at 6:36

answered Oct 31, 2014 at 6:27

user3378649

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2 Comments

user3440489 Over a year ago

Thanks for help. But this array of variable names is created using for loop as well using append (though this more elegant). Now what if I want to use these elements as variables and initialize them like a_true=45?

user3378649 Over a year ago

why u gave (-1) for all other answers. This solution solve the problem, but it's not the best. it should be ranked (0) in case u don't like it, (-x) for really unrelated soltion (which is not the case for this one or any of the others)

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