Python String Manipulation

Question

Having a hard time understanding what is happening in this snippet of code. Particularly with the 2nd line of code.

for line in infile:
 data = line.strip('\n').split(':')
 user_dict[data[0]] = data[1]

• kennytm: You mean the data = line? Which part of the line you don't understand?
• L. Ouyang: probably you mean the third line, because second line is quite straightforward. if you have trouble to understand second line, u could get help from docs.python.org/2/library/string.html, strip() means removing the leading and trailing character, in your case it means remove leading and trailing '\n'. For third line, data[0] and data[1] are both string, so it meas a dictionary named as user_dict, and its index is data[0] and its value is data[1].

Answer 1

The line sets the variable data equal to the string represented by the variable line with the new line character '\n' removed and then split anywhere a : occurs.

Answer 2

It parses a file having this structure:

a:52
b:hi
key:value

for line in infile: is a loop for each line in the file. Each line (except for the last maybe) ends with new-line symbol \n.

line.strip('\n') removes the new-line symbol.

.split(':') splits the string into strings there were separated by :. For example: "qwe:rty:uio".split(':') -> ["qwe", "rty", "uio"]

user_dict[data[0]] = data[1] obviously saves the data into the dicionary user_dict taking the first string as a key, and second one as a value.

For the file mentioned above this code creates the following dictionary:

{"a": "52", "b": "hi", "key": "value"}

Answer 3

line.strip('\n') is removing all the \n (new line) from the string and the split(':') it is going to split your string using : as the delimeter into an array of strings.

Answer 4

Above code is storing the file into the dictionary. Content of the file is like below

key1:value1
key2:value2
.
.
.
key3:value3

Second line is stripping off the \n character from the line and then splitting the each line by : character. However you should try to understand and debug the code line by line

Answer 5

line.strip('\n') will remove all the newlines from the string.

and

split(':') will split your string using ':' into array of strings.

• John Machin: line.strip doesn't do that ... see my comment above

Answer 6

data = line.strip('\n').split(':')

There are two string functions in one line. You also can separate the calls. This should be the same:

my_line = line.strip('\n')
my_line1 = my_line.split(':')

line.strip --> removes the new line character at the end of a line line.split(':') --> splits the values at colon character and return a list of each record

It is easier to understand with concrete values.

Your file look like this and you loop through each line. Name: Paul Age: 18 Gender: Male

At the end of each line you have a "new line" character which will remove line.strip('\n'). Then you split the values at ":" You finally create a dictionary (line 3) where key is the left side and the value is the right side. dict['Name'] = 'Paul' dict['Age'] = '18'

• John Machin: line.strip(newline) removes leading consecutive newlines and trailing consecutive newlines, but leaves embedded newlines alone. >>> "NNNtttNNNtttNNN".strip("N") produces 'tttNNNttt'

Answer 7

Basically line.strip('\n') removes leading consecutive newlines and trailing consecutive newlines, but leaves embedded newlines alone. from line; and then split(':') separates anywhere ":" is.This is then stored as a list in the variable named data.

• John Machin: line.strip doesn't do that ... see my comment on previous answer