Python String format() Method

19-01-23 Ahmed Obaid 1227 1
words: 573 | reading time: 6 minute

​The format() function formats complex strings more efficiently. By placing one or more surrogate fields inside a pair of curly braces {} in a string and calling the value we wish to put and concatenating it to the string.


How to formulate it like this:

using a single value.

{ }.format(value)

using multiple values.

{ } { } .format(value1, value2)

value : can be an integer, a float, a string, a character, or even a variable.

return value: Returns a new string formatted with the value passed as a parameter at the position of the field alt{} .

Errors and exceptions: Occurs when the string contains an additional surrogate field {} , and we have not passed any value to it.


Example:

# using format option in a simple string
print(" {} learn Python " .format("Hamza"))
# value stored in a variable
string = "You can learn {} and {} with Ahmed Obaid"
print(string.format("python", "django" )) 
# formatting a string using a numeric constant
print("I am {} years old !".format(38))

The output will be:

Hamza learn Python
You can learn python and django with Ahmed Obaid
I am 38 years old !

 Note: Alternate fields are the places to pass values ​​that are enclosed in curly braces {} .

 In the following example we will use multiple values ​​for several alternate fields.

 Example:

string = "I am {}, I will present on this site courses in {}, {}, and {}"
print(string.format("ahmed obaid","python", "django", "Data science"))

 The output will be:

I am ahmed obaid, I will present on this site courses in python, django, and Data science

 If the number of values ​​is more or less than the number of alternate fields, we will get an IndexError.

 Example:

string = "I am {}, I will present on this site courses in {}, {}, and {}"
print(string.format("python", "django", "Data science"))

 We will get this error:

Traceback (most recent call last):
  File "./prog.py", line 3, in <module>
IndexError: Replacement index 3 out of range for positional args tuple

 In the previous example, the number of values ​​was three: "python", "django", "Data science". And the number of alternative fields available four fields undefined So an error occurred.

 Also, the surrogate fields must be set with the index of the values ​​in order such as 0, 1, 2, 3… Observe the following example

 Example:

string = "I am {} {}  "
print(string.format("Ahmed", "obaid"))
string = "I am {} {}  "
print(string.format("obaid","Ahmed"))

 The output will be:

I am Ahmed obaid  
I am obaid Ahmed

 You can also pass the index numbers of the values ​​inside the brackets of the alternate fields. Where the starting index of the values ​​will be the number 0.

 Example:

# We have correctly ordered the index of values ​​with surrogate fields
string = "I am {0} {1}  "
print(string.format("Ahmed", "obaid"))
# Here we changed the index order of the values ​​with the surrogate fields
string = "I am {1} {0}  "
print(string.format("Ahmed", "obaid"))
# We have correctly ordered the index of values ​​with surrogate fields
string = "I am {0}, I will present on this site courses in {1}, {2}, and {3}"
print(string.format("Ahmed obaid", "python", "django", "Data science"))
# Here we changed the index order of the values ​​with the surrogate fields
string = "I am {0}, I will present on this site courses in {3}, {1}, and {2}"
print(string.format("Ahmed obaid", "python", "django", "Data science"))

 The output will be:

I am Ahmed obaid  
I am obaid Ahmed  
I am Ahmed obaid, I will present on this site courses in python, django, and Data science
I am Ahmed obaid, I will present on this site courses in Data science, python, and django

 External sources:

 Built-in functions - official Python documentation

 If you have any questions or concerns, leave them in the comments

Tags

Python python data types Python String string methods python python string format method

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