C++ for-loop vs. Python for-loop

Question

I\'m currently learning Python as I\'m taking a data mining class. I was making a for-loop to make a noisy data file to do smoothing and I found a peculiarity on Python for-

Answer 1

First, replicating a c/c++ structure is not the best way to approach solving a problem. You will inevitably end up fighting against the language instead of benefiting from its strengths.

Secondly, to convert a c/c++ for loop, you have to realize that it is actually a while in disguise:

for (<initialization>,<condition>,<increment>)
{
    // your stuff
}

Because Python for loops override the control variable (i) at each iteration, they can not translate directly to C/C++ loops that modify the control variable within their code block. These kinds of loops translate to this in Python (which is unwieldy and cumbersome):

<initialization>
while <condition>:
     # your stuff
     <increment>

for your particular example:

i = 0
while i < len(input):
   # ...
   i += 1

A more pythonic translation of you code would look more like this:

eachword = ''
for character in input:
    if  character in [' ','\0']: # will drop last word because no \0 at end of strings
        print(eachword)
        eachword = ''
    else:
        eachword += character 

strings in python don't have a nul character at the end so the last word will likely be dropped unless your input comes from a non-standard source

Python has a built-in function to separate words in a string:

for eachword in input.split():
    print(eachword)

Answer 2

There are two main problems with the python I see;

Firstly the for loop does not work in the same way as the cpp for loop: python will reset i to go through the range, what you did with i inside the previous loops will be lost. Secondly python does not have a termination char on its strings like cpp does:

input = "abc defg"
eachWord = ''

i = 0
while(i < len(input)):
    print("At the first part of the loop, i = ", i, ".")
    while(i < len(input) and input[i] != ' '):
        eachWord += input[i]
        i += 1

    print(eachWord)
    print("At the last part of the loop, i = ", i, ".")
    print()
    eachWord = ''
    i += 1